Remove useK2 property

#KT-64380
diff --git a/libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/kotlin/org/jetbrains/kotlin/gradle/Kapt3IT.kt b/libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/kotlin/org/jetbrains/kotlin/gradle/Kapt3IT.kt
index 5be4d26..4964dcf 100644
--- a/libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/kotlin/org/jetbrains/kotlin/gradle/Kapt3IT.kt
+++ b/libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/kotlin/org/jetbrains/kotlin/gradle/Kapt3IT.kt
@@ -156,10 +156,6 @@
     override fun testMultipleProcessingPasses(gradleVersion: GradleVersion) {
     }
 
-    @Disabled("classloaders cache is leaking file descriptors that prevents cleaning test project")
-    override fun useK2KaptProperty(gradleVersion: GradleVersion) {
-    }
-
     override fun testAnnotationProcessorAsFqName(gradleVersion: GradleVersion) {
         project("annotationProcessorAsFqName".withPrefix, gradleVersion) {
             //classloaders caching is not compatible with includeCompileClasspath
@@ -1340,41 +1336,6 @@
         }
     }
 
-    @DisplayName("K2 Kapt can be enabled via Gradle property kapt.use.k2")
-    @GradleTest
-    open fun useK2KaptProperty(gradleVersion: GradleVersion) {
-        project("simple".withPrefix, gradleVersion) {
-            buildGradle.appendText(
-                """
-                |tasks.withType(org.jetbrains.kotlin.gradle.tasks.KotlinCompile).configureEach {
-                |    compilerOptions {
-                |        freeCompilerArgs.addAll([
-                |            "-Xuse-fir-ic",
-                |            "-Xuse-fir-lt"
-                |        ])
-                |    }
-                |    kotlinOptions {
-                |        languageVersion = "2.0"
-                |    }
-                |}
-                |
-                |compileKotlin.kotlinOptions.allWarningsAsErrors = false
-                """.trimMargin()
-            )
-            build("-Pkapt.use.k2=true", "build") {
-                assertKaptSuccessful()
-                assertTasksExecuted(":kaptGenerateStubsKotlin", ":kaptKotlin", ":compileKotlin")
-                assertOutputDoesNotContain("Falling back to 1.9.")
-                assertOutputContains("K2 kapt is an experimental feature. Use with caution.")
-            }
-            build("-Pkapt.use.k2=true", "cleanCompileKotlin", "compileKotlin") {
-                assertTasksExecuted(":compileKotlin")
-                // The warning should not be displayed for the compile task.
-                assertOutputDoesNotContain("K2 kapt is an experimental feature. Use with caution.")
-            }
-        }
-    }
-
     @DisplayName("Kapt-generated Kotlin sources can be used in Kotlin")
     @GradleTest
     open fun useGeneratedKotlinSource(gradleVersion: GradleVersion) {
diff --git a/libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/kotlin/org/jetbrains/kotlin/gradle/Kapt4IT.kt b/libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/kotlin/org/jetbrains/kotlin/gradle/Kapt4IT.kt
index 216376f..51d4715 100644
--- a/libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/kotlin/org/jetbrains/kotlin/gradle/Kapt4IT.kt
+++ b/libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/kotlin/org/jetbrains/kotlin/gradle/Kapt4IT.kt
@@ -30,9 +30,6 @@
     @Disabled("Doesn't make sense in Kapt 4")
     override fun fallBackModeWithLanguageVersion2_0(gradleVersion: GradleVersion) {}
 
-    @Disabled("Doesn't make sense in Kapt 4")
-    override fun useK2KaptProperty(gradleVersion: GradleVersion) {}
-
     @DisplayName("KT-61879: K2 KAPT works with proguarded compiler jars and enum class")
     @GradleTest
     fun testEnumClass(gradleVersion: GradleVersion) {
diff --git a/libraries/tools/kotlin-gradle-plugin/src/common/kotlin/org/jetbrains/kotlin/gradle/internal/kapt/Kapt3KotlinGradleSubplugin.kt b/libraries/tools/kotlin-gradle-plugin/src/common/kotlin/org/jetbrains/kotlin/gradle/internal/kapt/Kapt3KotlinGradleSubplugin.kt
index 1592c2a..3db3b84 100644
--- a/libraries/tools/kotlin-gradle-plugin/src/common/kotlin/org/jetbrains/kotlin/gradle/internal/kapt/Kapt3KotlinGradleSubplugin.kt
+++ b/libraries/tools/kotlin-gradle-plugin/src/common/kotlin/org/jetbrains/kotlin/gradle/internal/kapt/Kapt3KotlinGradleSubplugin.kt
@@ -25,7 +25,6 @@
 import org.jetbrains.kotlin.gradle.internal.Kapt3GradleSubplugin.Companion.isInfoAsWarnings
 import org.jetbrains.kotlin.gradle.internal.Kapt3GradleSubplugin.Companion.isKaptKeepKdocCommentsInStubs
 import org.jetbrains.kotlin.gradle.internal.Kapt3GradleSubplugin.Companion.isKaptVerbose
-import org.jetbrains.kotlin.gradle.internal.Kapt3GradleSubplugin.Companion.isUseK2
 import org.jetbrains.kotlin.gradle.model.builder.KaptModelBuilder
 import org.jetbrains.kotlin.gradle.plugin.*
 import org.jetbrains.kotlin.gradle.plugin.mpp.KotlinJvmAndroidCompilation
@@ -123,10 +122,6 @@
             return getBooleanOptionValue(BooleanOption.KAPT_KEEP_KDOC_COMMENTS_IN_STUBS)
         }
 
-        fun Project.isUseK2(): Boolean {
-            return getBooleanOptionValue(BooleanOption.KAPT_USE_K2)
-        }
-
         fun Project.classLoadersCacheSize(): Int = findPropertySafe(CLASSLOADERS_CACHE_SIZE)?.toString()?.toInt() ?: 0
 
         fun Project.disableClassloaderCacheForProcessors(): Set<String> {
@@ -218,7 +213,6 @@
             KAPT_INFO_AS_WARNINGS("kapt.info.as.warnings", false),
             KAPT_INCLUDE_COMPILE_CLASSPATH("kapt.include.compile.classpath", true),
             KAPT_KEEP_KDOC_COMMENTS_IN_STUBS("kapt.keep.kdoc.comments.in.stubs", true),
-            KAPT_USE_K2("kapt.use.k2", false),
         }
     }
 
@@ -538,7 +532,6 @@
     pluginOptions += SubpluginOption("keepKdocCommentsInStubs", "${project.isKaptKeepKdocCommentsInStubs()}")
     pluginOptions += SubpluginOption("showProcessorTimings", "${kaptExtension.showProcessorStats}")
     pluginOptions += SubpluginOption("detectMemoryLeaks", kaptExtension.detectMemoryLeaks)
-    pluginOptions += SubpluginOption("useK2", "${project.isUseK2()}")
     pluginOptions += SubpluginOption("infoAsWarnings", "${project.isInfoAsWarnings()}")
     pluginOptions += FilesSubpluginOption("stubs", kaptStubsDir)
 
diff --git a/libraries/tools/kotlin-gradle-plugin/src/common/kotlin/org/jetbrains/kotlin/gradle/internal/kapt/KaptGenerateStubsTask.kt b/libraries/tools/kotlin-gradle-plugin/src/common/kotlin/org/jetbrains/kotlin/gradle/internal/kapt/KaptGenerateStubsTask.kt
index 77cd249..03529de 100644
--- a/libraries/tools/kotlin-gradle-plugin/src/common/kotlin/org/jetbrains/kotlin/gradle/internal/kapt/KaptGenerateStubsTask.kt
+++ b/libraries/tools/kotlin-gradle-plugin/src/common/kotlin/org/jetbrains/kotlin/gradle/internal/kapt/KaptGenerateStubsTask.kt
@@ -75,9 +75,6 @@
     @get:Input
     abstract val verbose: Property<Boolean>
 
-    @get:Input
-    abstract val useK2Kapt: Property<Boolean>
-
     /**
      * Changes in this additional sources will trigger stubs regeneration,
      * but the sources themselves will not be used to find kapt annotations and generate stubs.
@@ -138,10 +135,6 @@
 
             args.verbose = verbose.get()
             args.destinationAsFile = destinationDirectory.get().asFile
-
-            if (useK2Kapt.get()) {
-                args.freeArgs += "-Xuse-kapt4"
-            }
         }
 
         pluginClasspath { args ->
@@ -163,5 +156,5 @@
     }
 
     override fun isIncrementalCompilationEnabled(): Boolean =
-        super.isIncrementalCompilationEnabled() && !useK2Kapt.get() && ("-Xuse-kapt4" !in compilerOptions.freeCompilerArgs.get())
+        super.isIncrementalCompilationEnabled() && ("-Xuse-kapt4" !in compilerOptions.freeCompilerArgs.get())
 }
diff --git a/libraries/tools/kotlin-gradle-plugin/src/common/kotlin/org/jetbrains/kotlin/gradle/tasks/configuration/KaptGenerateStubsConfig.kt b/libraries/tools/kotlin-gradle-plugin/src/common/kotlin/org/jetbrains/kotlin/gradle/tasks/configuration/KaptGenerateStubsConfig.kt
index ca9a736..8cd34b6 100644
--- a/libraries/tools/kotlin-gradle-plugin/src/common/kotlin/org/jetbrains/kotlin/gradle/tasks/configuration/KaptGenerateStubsConfig.kt
+++ b/libraries/tools/kotlin-gradle-plugin/src/common/kotlin/org/jetbrains/kotlin/gradle/tasks/configuration/KaptGenerateStubsConfig.kt
@@ -16,7 +16,6 @@
 import org.jetbrains.kotlin.gradle.internal.*
 import org.jetbrains.kotlin.gradle.internal.Kapt3GradleSubplugin.Companion.KAPT_SUBPLUGIN_ID
 import org.jetbrains.kotlin.gradle.internal.Kapt3GradleSubplugin.Companion.isIncludeCompileClasspath
-import org.jetbrains.kotlin.gradle.internal.Kapt3GradleSubplugin.Companion.isUseK2
 import org.jetbrains.kotlin.gradle.plugin.KaptExtension
 import org.jetbrains.kotlin.gradle.plugin.KotlinCompilation
 import org.jetbrains.kotlin.gradle.plugin.KotlinCompilationInfo
@@ -50,7 +49,6 @@
         configureTask { task ->
             task.verbose.set(KaptTask.queryKaptVerboseProperty(project))
             task.pluginOptions.add(buildOptions(kaptExtension, task))
-            task.useK2Kapt.value(project.isUseK2()).finalizeValueOnRead()
 
             if (!isIncludeCompileClasspath(kaptExtension)) {
                 task.onlyIf {