[Model Averaging] Remove unused variable world_size in post_localSGD_hook.py (#74803)
Summary:
As title
Pull Request resolved: https://github.com/pytorch/pytorch/pull/74803
Reviewed By: albanD
Differential Revision: D35175613
Pulled By: mrshenli
fbshipit-source-id: 881933656ed214554b8acb4c5756349cea0af51d
(cherry picked from commit 033efb2eea856d00d5e78c8a99d726c6cf69d714)
