[Docs] Fix typo in RPC docs (#35809)
Summary:
It's also fixed in the cherry pick PR https://github.com/pytorch/pytorch/pull/35808
Pull Request resolved: https://github.com/pytorch/pytorch/pull/35809
Differential Revision: D20803338
Pulled By: rohan-varma
fbshipit-source-id: 1925f367703faf053ab4b1c0ff0acb86230c5d89
