[clang] [clang] reject to capture variable in `RequiresExprBodyDecl` (PR #78598)

[Younan Zhang via cfe-commits]

zyn0217 wrote:

I think this also fixes https://github.com/llvm/llvm-project/issues/63845 and the example in https://github.com/llvm/llvm-project/issues/41751#issuecomment-1696389046.

https://github.com/llvm/llvm-project/pull/78598