[clang] [Clang] Properly parse enumeration declarations with fixed underlying type in generic associations (PR #210353)

[Abdulmalek Almkainzi via cfe-commits]

aalmkainzi wrote:

thinking about it, should I use `isTypeSpecifierQualifier` instead of `isCXXTypeId`? that way the `int{C}` thing won't be a problem.

https://github.com/llvm/llvm-project/pull/210353