Reorder gc.py imports (#57779)
Summary:
A tiny PR that reorder imports and run autopep8
Pull Request resolved: https://github.com/pytorch/pytorch/pull/57779
Reviewed By: malfet
Differential Revision: D28269455
Pulled By: samestep
fbshipit-source-id: 7d3176efad96e3a8ac1cdc76a5018c7ffa00c449
