Minor RPC doc fixes (#43337)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/43337
Test Plan: Imported from OSS
Reviewed By: osalpekar
Differential Revision: D23242698
Pulled By: osalpekar
fbshipit-source-id: 7757fc43824423e3a6efd4da44c69995f64a6015
