[clang] [Clang] fix generic lambda inside requires-clause of friend function template (PR #99813)

[Matheus Izvekov via cfe-commits]

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

The assert was never added to the template template parameter case, but I think a test case might be good here.

But in any case this LGTM.

https://github.com/llvm/llvm-project/pull/99813