[clang] [Clang] Fix parsing of invalid type-requirement (PR #98545)

[Younan Zhang via cfe-commits]

https://github.com/zyn0217 approved this pull request.

Thanks! This makes sense to me.
(Curiously GCC and MSVC seem to defer the check until the evaluation. However, I don't think we have to do that in this patch anyway.)

https://github.com/llvm/llvm-project/pull/98545