[Gradient Compression] Fix PowerSGD docstring by removing an extra whitespace (#55666)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/55666
{F590513307}
Some code is not properly displayed due to an extra whitespace ahead of `(num_rows + num_cols)`.
ghstack-source-id: 126148569
Test Plan: Locally viewed
Reviewed By: rohan-varma
Differential Revision: D27673663
fbshipit-source-id: 603ae4ddbe86ceaefc311885b82b0f6b48b57b27
