Remove unused param in Caffe2 LayerNormGradientOp (#22282)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/22282
Remove unused param in Caffe2 LayerNormGradientOp
Reviewed By: bddppq, houseroad
Differential Revision: D16017117
fbshipit-source-id: bdd0bd2aca009e549dfd2bf622494dfc791589e3
