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

[via cfe-commits]

https://github.com/cor3ntin approved this pull request.

LGTM (for the time being, I don't think this is workable long term)

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