[clang] [Clang][Sema] Fix bug where operator-> typo corrects in the current instantiation (PR #91972)

[Krystian Stasiowski via cfe-commits]

sdkrystian wrote:

> I think this needs a release note? I know the only case we have right now is because of your other patch, but perhaps this affects elsewhere too?

@erichkeane I don't think we need a release note since the code changes are in `LookupMemberExpr`, which prior to #90152 had no valid code path for dependent types (and had the assert `assert(!BaseType->isDependentType())` to ensure this).

https://github.com/llvm/llvm-project/pull/91972