[clang] [Clang][Sema] Revisit the fix for the lambda within a type alias template decl (PR #89934)

[Matheus Izvekov via cfe-commits]

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

I agree this is not the long term way forward, but it improves the current interim solution, so LGTM, minus nit.

https://github.com/llvm/llvm-project/pull/89934