[Model Averaging] Fix docstring of PeriodicModelAverager (#62392)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/62392
The constructor of `PeriodicModelAverager` does not need to accept parameters.
ghstack-source-id: 134626245
Test Plan: buck test mode/dev-nosan caffe2/test/distributed:distributed_nccl_fork -- test_periodic_model_averager
Reviewed By: rohan-varma
Differential Revision: D29986446
fbshipit-source-id: 6a8b709e4383a3c44b9e60955fbb067cd2868e76