Polish rpc docstring. (#30069)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/30069
1) Fix rpc docstrings
2) Fix some links
ghstack-source-id: 94250890
Test Plan: waitforbuildbot
Differential Revision: D18588231
fbshipit-source-id: 33846ace1afa94d25f34b0370437abf6d9408f06
