[clang] [clang] Remove the EnableLifetimeWarnings flag in lifetime analysis. (PR #105884)

[Gábor Horváth via cfe-commits]

https://github.com/Xazax-hun approved this pull request.

Thanks, this is a nice cleanup, but I'd prefer either the PR to be split up, or renamed to emphasize the bug fix aspect of the PR. 

https://github.com/llvm/llvm-project/pull/105884