Add pixel_shuffle to core aten decomps (#120092)
Summary:
https://github.com/pytorch/pytorch/pull/118239 added a decomposition
for pixel_shuffle, so pixel_shuffle no longer needs to be a Core ATen Op. We
have also fixed the internal use case so that it no longer special cases on
pixel_shuffle, allowing us to revert the changes in
https://github.com/pytorch/pytorch/pull/118921.
Test Plan: CI
Differential Revision: D53860966
Pull Request resolved: https://github.com/pytorch/pytorch/pull/120092
Approved by: https://github.com/ydwu4
