[Test] Disable UNUSED_* diagnostics in tests which are not belong to contolFlowAnalysis suite

compiler/testData/diagnostics/tests/generics/varProjection/setterProjectedOutPlusAssignDefined.kt

@@ -1,13 +1,14 @@
+// FIR_IDENTICAL
 // !DIAGNOSTICS: -UNREACHABLE_CODE
 interface Tr<T> {
     var v: T
 }
 
 class C {
-    operator fun plusAssign(<!UNUSED_PARAMETER!>c<!>: C) {}
+    operator fun plusAssign(c: C) {}
 }
 
 fun test(t: Tr<out C>) {
     // No error because no real assignment happens
     t.v += null!!
-}
+}