[clang] [clang][Sema] Deprecate `global`/`unknown` in `lifetime_capture_by` (PR #196635)

[via cfe-commits]

NeKon69 wrote:

Well it doesn't quite *break* anything it just shows a deprecation warning, you still can use the attribute with that parameter as you used it before. But if you want warning-free code then you should just replace all occurances of `lifetime_capture_by(this)` with `lifetime_capture_by_this` (as noted in the warning that is emitted when you use `lifetime_capture_by(this)`)

https://github.com/llvm/llvm-project/pull/196635