Fix typos in RPC Docs (#40219)
Summary:
Environment variable MASTER_ADDRESS and MASTER_port should be MASTER_ADDR and MASTER_PORT respectively.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/40219
Differential Revision: D22116585
Pulled By: mrshenli
fbshipit-source-id: d312ae66210b0a16ec3ab1f468b1654bb0a75a0f
