Constant prop prim::None (#15979)
Summary:
Previously we were only constant propping prim::Constants, but we should be constant propping prim::None as well.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/15979
Differential Revision: D13664692
Pulled By: eellison
fbshipit-source-id: 01839403576c21fc030c427e49275b8e1210fa8f
