Add compare_set in distributed docs (#61351)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/61351
Test Plan: Imported from OSS
Reviewed By: mrshenli
Differential Revision: D29588206
Pulled By: H-Huang
fbshipit-source-id: 9db48e7b6de29503275f10616470ad2d66b075f9
