[FIR] Fix inconsistent RETURN_TYPE_MISMATCH and TYPE_MISMATCH reporting on functions and properties

^KT-51203 Fixed

compiler/testData/diagnostics/tests/regressions/OutProjections.fir.kt

@@ -8,7 +8,7 @@ fun <T> f(expression : T) : G<out T> = G<T>()
 
 fun foo() : G<Point> {
   val p = Point()
-  return <!RETURN_TYPE_MISMATCH, TYPE_MISMATCH!>f<Point>(p)<!>
+  return <!RETURN_TYPE_MISMATCH!>f<Point>(p)<!>
 }
 
 class Out<out T>() {}