Fix lint issues in dist_autograd_test.py (#30928)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/30928
ghstack-source-id: 95152373
Test Plan: waitforbuildbot
Differential Revision: D18872870
fbshipit-source-id: 2cd1ef228da4bd90c13e2f067a0c89b975fa3179
