Also remove incorrect subtype check checkers
Test unsafeVarianceInAliasedFunctionalType.kt started to fail because
of KT-54894. This bug existed before, changes from this commit just
unhided it (previously it was hidden because incorrect subtype check
in `isSubtypeForTypeMismatch` which is used by FirFunctionReturnTypeMismatchChecker
This directive anyway does not make test run twice with OI, and with NI
It only once run the test with specific settings (// LANGUAGE)
and ignores irrelevant (OI or NI tags)