Fix typo in name of LayerNormBackwardCUDAKernel (#66000)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/66000
Saw this in nvprof and I'm just a little too nitpicky to let it slide!
ghstack-source-id: 139547271
Test Plan: CI
Reviewed By: xiaomengy
Differential Revision: D31340262
fbshipit-source-id: ab48dc99c34a74585e66800b4bbcccc6aabbaff2
