KT-47475 Do not copy InnerClass attribute for WhenMapping classes

compiler/backend/src/org/jetbrains/kotlin/codegen/inline/ObjectTransformer.kt

@@ -83,6 +83,13 @@ class WhenMappingTransformer(
                     methodNodes.add(this)
                 }
             }
+
+            override fun visitInnerClass(name: String?, outerName: String?, innerName: String?, access: Int) {
+                // Drop the attribute as the recreated class is not an inner class of the original outer class.
+                // In principle, we could also generate a new attribute with outerName set to the caller-side class,
+                // but that would require modification of both the inner (recreated) and the outer (caller-side) classes.
+                // The latter would require a lot of work without any clear benefits.
+            }
         }, ClassReader.SKIP_FRAMES)
 
         assert(methodNodes.size == 1) {