[clang] [Sema][NFC] Move two misplaced uninit tests to clang/test/SemaCXX (PR #128013)

[Donát Nagy via cfe-commits]

NagyDonat wrote:

I'm merging this now because I feel that the current reviews are sufficient for this simple NFC change. If there are any further observations/suggestions, feel free to mention them -- I can address them in a follow-up commit. 

https://github.com/llvm/llvm-project/pull/128013