[LocalSGD] Move feature to Beta, clean up some docs (#71621)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/71621
Moves this feature to beta as discussed, and cleans up some docs.
Synced offline with wayi1 who mentioned that the current names are preferred
as he works to prototype hierarchical allreduce as discussed in this RFC: https://github.com/pytorch/pytorch/issues/71325.
ghstack-source-id: 147382940
Test Plan: CI
Reviewed By: zhaojuanmao
Differential Revision: D33700444
fbshipit-source-id: 8eb543f5b02a119d0790a5c0919e6def6383a067
(cherry picked from commit 656e9809b2429d1924e008164a1f4ca770700a9a)
