[clang] [clang] Fix sema on ObjCLifetime conversion (PR #178524)

[Aaron Ballman via cfe-commits]

AaronBallman wrote:

> I don't think should have been merged w/o a comment from @ojhunt that his concerns were properly addressed. If you are waiting to hear back you should have brought in another clang frontend maintainer e.g. @AaronBallman @erichkeane @cor3ntin

+1, changes should not be landed when a reviewer has marked that they're requesting changes. This is particularly important because these changes are to lifetime rules. I think a revert would be appropriate just to make sure there's comfort with the changes.

I don't feel comfortable reviewing this, but @ahatanak is our Objective-C conformance maintainer.

https://github.com/llvm/llvm-project/pull/178524