[clang] [clang] Update the lifetimebound example with up-to-date expected warning and change the sample code to be a fully working example (PR #113437)

[Shafik Yaghmour via cfe-commits]

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

LGTM, other than the minor comment.

https://github.com/llvm/llvm-project/pull/113437