Summary: PyTorch 1.7.0 was in Oct 2020 and 1.7.1 was in Dec 2020. We shouldn't need older than them, maybe not even 1.7.0.

Reviewed By: patricklabatut

Differential Revision: D33507967

fbshipit-source-id: d3de09c20c44870cbe5522705f2293acc0e62af3