[clang] [Clang][Sema] Fix malformed AST for anonymous class access in template. (PR #90842)

[via cfe-commits]

martinboehme wrote:

CI failure (DataFlowSanitizer-x86_64 :: release_shadow_space.c) looks unrelated.

Will merge now. @shafik If you have any remaining comments, happy to address those in a followup PR.

https://github.com/llvm/llvm-project/pull/90842