[clang] [Clang][Sema] fix a bug on constraint check with template friend function (PR #90646)

[Erich Keane via cfe-commits]

https://github.com/erichkeane commented:

This seems reasonable, @mizvekov is doing more work in this area, so I'd like him to make sure this isn't something he's fixed elsewhere.

https://github.com/llvm/llvm-project/pull/90646