[clang] [Clang][Sema] Fix regression due to missing ambiguity check before attempting access check. (PR #80730)

[Erich Keane via cfe-commits]

https://github.com/erichkeane approved this pull request.

This'll need a cherry pick to 18 as it is a break against 17, right?  Otherwise LGTM.

https://github.com/llvm/llvm-project/pull/80730