[Gradient Compression] Update the docstring of fp16_compress_wrapper (#53955)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/53955
Per title
ghstack-source-id: 123852836
Test Plan: N/A
Reviewed By: iseessel
Differential Revision: D27032700
fbshipit-source-id: 6f9bbc028efe6cc9b54f4ec729fea745368efb2e
