[clang] [clang] fix deduction of member pointers with dependent named classes (PR #133113)

[Matheus Izvekov via cfe-commits]

mizvekov wrote:

Note this was unrelated to another regression, as reported here: https://github.com/llvm/llvm-project/pull/132317#issuecomment-2755417893

Since this fixes a regression which recently landed, I am going to go ahead and merge, relying on post-commit review.

https://github.com/llvm/llvm-project/pull/133113