[JIT] peephole optimize values with NoneType (#33264)
Summary:
If a value has the type None, we can always replace it with a None constant.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/33264
Differential Revision: D19878695
Pulled By: eellison
fbshipit-source-id: 5d0e7ffb37c5747997df093fec3183039d8dff4d
