Minor format cleanup in py_rref.cpp (#37520)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/37520
Test Plan: Imported from OSS
Reviewed By: xush6528
Differential Revision: D21308889
Pulled By: mrshenli
fbshipit-source-id: 36d5efc4d9c3e6cc0b2abec35675a338a2f81424
