Retiring _module_copies field in DDP reducer. (#59094)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/59094
Commented out _module_copies fields and changed for loops accordingly
Test Plan: Test cases mentioned in T91292908 passed succesfully
Reviewed By: SciPioneer
Differential Revision: D28736135
fbshipit-source-id: 1857102f0c57a734026f3025e9653d8fad57d0b6
