[compiler-rt] [clang] [mlir] [llvm] [clang-tools-extra] [clang] Fix a bug with qualified name lookup into current instantiation (PR #73018)

[Mariya Podchishchaeva via cfe-commits]

Fznamznon wrote:

I'm not sure I understand why gcc is giving an error in  https://godbolt.org/z/qGfnzhfsK. It doesn't give an error with `typename` keyword and I think there shouldn't be any difference since `Y::E` refers to current instantiation and is being used by class member declaration so no `typename` required.
cc @shafik @cor3ntin @zygoloid for an opinion.

https://github.com/llvm/llvm-project/pull/73018