FIR: add temporary access to Enum.getDeclaringClass (see KT-49653)

compiler/testData/codegen/box/enum/declaringClassOnEnumObject.kt

@@ -1,6 +1,4 @@
 // TARGET_BACKEND: JVM
-// IGNORE_BACKEND_FIR: JVM_IR
-// FIR status: UNRESOLVED_REFERENCE (declaringClass). See https://youtrack.jetbrains.com/issue/KT-49653. To be discussed.
 package test
 
 enum class KEnum { A }