Remove unnecessary pickle and unpickle invocation in PyRRef __setstate__/__getstate__ methods (#37638)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/37638
Test Plan: Imported from OSS
Differential Revision: D21343280
Pulled By: mrshenli
fbshipit-source-id: da462fee5815dc74c7f2dc3161699e461bc7d7d3
