[FIR] Fix generating this reference in delegated accessors

There was a problem with delegated extension property with dispatch
  receiver that `this` in `getValue` call was set to dispatch receiver
  instead of extension one

compiler/testData/codegen/box/ir/serializationRegressions/deepGenericDelegatedProperty.kt

@@ -1,6 +1,5 @@
 // DONT_TARGET_EXACT_BACKEND: WASM
 // WASM_MUTE_REASON: PROPERTY_REFERENCES
-// IGNORE_BACKEND_FIR: JVM_IR
 // IGNORE_BACKEND: NATIVE
 //For KT-6020
 
@@ -59,4 +58,4 @@ fun box(): String {
     val p = Value("O", CR("K"))
     val rr = p.additionalText
     return rr.p1 + rr.p2
-}
+}