[FIR] Don't enhance Int and String Java final static fields

It's effectively a breaking change (^KT-62558)

K2 assigns flexible type to all static fields (from Java) and, for example,
`String? becomes String unlike K1. It affects IR signature generating.
That's why signature dump is disabled for some tests.

^KT-57811 Fixed
^KT-61786 Fixed

compiler/testData/ir/irText/firProblems/SameJavaFieldReferences.kt

@@ -1,5 +1,4 @@
 // TARGET_BACKEND: JVM
-// FIR_IDENTICAL
 // FILE: SomeJavaClass.java
 
 public class SomeJavaClass {