Update floor_divide behavior in line with NumPy 1.20 (#56893)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/56893
Fixes gh-56814
Test Plan: Imported from OSS
Reviewed By: ngimel
Differential Revision: D28025814
Pulled By: mruberry
fbshipit-source-id: 8654978ea1d5aa7c12bcf5a8c939966287a2d34e
