[NCCL Docs] Adding Comments for Work-level Finish in ProcessGroup (#40404)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/40404
Adds docs to the finish function in ProcessGroup::Work. It's better to have some documentation around these functions since we have some PR's with API-changes/optimizations for these work-level functions here and in the subclasses.
ghstack-source-id: 106381736
Test Plan: CI (Docs change only)
Differential Revision: D22174891
fbshipit-source-id: 7901ea3b35caf6f69f37178ca574104d3412de28
