Removed asserts for mirror files for java stubs on kt files

The behavior of this part of code is following:
1) We wrap the kotlin light class to the object that wraps the kt files into compiled (!) cls stub (notice, that most of the time it is a single file wrapper)
2) Platform wishes to get the mirror psi of this "compiled" stub work with text of it.
3) Platform request mirror element that asserted to be ok ONLY for multifiles stub.
4) It leads to EA-209577

There is no idea why so, but the exception is high-rated, so this assertion was deleted.

Fixed EA-209577
diff --git a/compiler/light-classes/src/org/jetbrains/kotlin/asJava/builder/LightClassBuilder.kt b/compiler/light-classes/src/org/jetbrains/kotlin/asJava/builder/LightClassBuilder.kt
index 0ff5bd3..54ed687 100644
--- a/compiler/light-classes/src/org/jetbrains/kotlin/asJava/builder/LightClassBuilder.kt
+++ b/compiler/light-classes/src/org/jetbrains/kotlin/asJava/builder/LightClassBuilder.kt
@@ -91,20 +91,6 @@
 
         override fun isPhysical() = false
 
-        override fun appendMirrorText(indentLevel: Int, buffer: StringBuilder) {
-            if (files.size == 1) {
-                LOG.error("Mirror text should never be calculated for light classes generated from a single file")
-            }
-            super.appendMirrorText(indentLevel, buffer)
-        }
-
-        override fun getMirror(): PsiElement {
-            if (files.size == 1) {
-                LOG.error("Mirror element should never be calculated for light classes generated from a single file")
-            }
-            return super.getMirror()
-        }
-
         override fun getText(): String {
             return files.singleOrNull()?.text ?: super.getText()
         }