[DDP][ez] Remove misleading comment (#62230)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/62230
We don't iterate over model replicas anymore.
ghstack-source-id: 134475834
Test Plan: CI
Reviewed By: SciPioneer
Differential Revision: D29918760
fbshipit-source-id: 84bde670b4e91667a49f94f1b597fad364498467
