[Gradient Compression] Update _powerSGD_comm_hook_wrapper to only expose 2 most critical hyperparameters (#55295)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/55295
Update `_powerSGD_comm_hook_wrapper` to only expose 2 most critical hyperparameters, to make this API more clear to any future user (although the second hyperparameter `start_powerSGD_iter` is not in use yet).
Test Plan: waitforbuildbot
Reviewed By: shuyingsunshine21
Differential Revision: D27561734
fbshipit-source-id: b661981cc033b109f4f2fc92b435567a184a7fb5
