[PyTorch Docs] Updated RRef docs to indicate RPC Retries (#36678)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/36678
Updated the docs to explicitly indicate that RRef control messages are
idempotent and retried upon failure.
ghstack-source-id: 102225791
Test Plan: build bot
Differential Revision: D20828041
fbshipit-source-id: ca4d71c65a453664c16c32134c47637a966b1a19
