FIR: Update test data (repeated diagnostics)

They are a bit redundant, but it needs additional work to be done
to avoid them

compiler/testData/diagnostics/tests/inference/regressions/kt2841_this.kt

@@ -1,4 +1,3 @@
-// FIR_IDENTICAL
 // !WITH_NEW_INFERENCE
 
 package a
@@ -18,4 +17,4 @@ fun test() {
         this.close()
         <!UNRESOLVED_REFERENCE!>x<!>
     }
-}
+}