K2: report PLATFORM_CLASS_MAPPED_TO_KOTLIN with corresponding Kotlin class

...in lieu of the current user-given platform class

^KTIJ-29590

compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/extra/PlatformClassMappedToKotlinImportsChecker.kt

diff --git a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/extra/PlatformClassMappedToKotlinImportsChecker.kt b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/extra/PlatformClassMappedToKotlinImportsChecker.kt
index cf97d4c..900de17 100644
--- a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/extra/PlatformClassMappedToKotlinImportsChecker.kt
+++ b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/extra/PlatformClassMappedToKotlinImportsChecker.kt
@@ -28,7 +28,7 @@
 
             val kotlinClass = context.session.platformClassMapper.getCorrespondingKotlinClass(classId)
             if (kotlinClass != null) {
-                reporter.reportOn(import.source, FirErrors.PLATFORM_CLASS_MAPPED_TO_KOTLIN, classId, context)
+                reporter.reportOn(import.source, FirErrors.PLATFORM_CLASS_MAPPED_TO_KOTLIN, kotlinClass, context)
             }
         }
     }