Remove req to call step() in training loop (#63164)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/63164
Test Plan: Imported from OSS
Reviewed By: mrshenli
Differential Revision: D30284616
Pulled By: andwgu
fbshipit-source-id: afdb677fb08851b139178a9f6d782196f26773e1
