Use [[deprecated]] instead of C10_DEPRECATED (#30918)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/30918
This is a C++14 feature we can use now
ghstack-source-id: 95811482
Test Plan: waitforsandcastle
Differential Revision: D18869636
fbshipit-source-id: b5b3d78b61b6ceb2deda509131f8502e95b1d057
