[clang] [NFC][Clang] Simplify getTrailingObjects for OpenACC/OpenMP Clause (PR #139838)

[Erich Keane via cfe-commits]

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

@alexey-bataev for visibility as he's the OMP owner.

https://github.com/llvm/llvm-project/pull/139838