[FIR] Generate signatures for synthesized class delegation fields

This is to align the behavior with K1.

^KT-57754 Fixed

Co-authored-by: Alexander Udalov <alexander.udalov@jetbrains.com>

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

@@ -1,8 +1,5 @@
 // TARGET_BACKEND: JVM
 
-// MUTE_SIGNATURE_COMPARISON_K2: ANY
-// ^ KT-57754
-
 // FILE: Foo.java
 
 import java.util.Set;