[PyTorch] Mark borrowed case as C10_LIKELY in MaybeOwned (#55553)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/55553
If this case isn't likely, user code would have been better off with a regular T.
ghstack-source-id: 126369326
Test Plan: Existing CI
Reviewed By: ezyang
Differential Revision: D27630287
fbshipit-source-id: b074af3a65c61dfe9e0246df046cc8c49e8efb03
