[GPU] Clean up the operator tests (#50311)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/50311
Code clean up
ghstack-source-id: 119693032
Test Plan: Sandcastle
Reviewed By: husthyc
Differential Revision: D25823635
fbshipit-source-id: 5205ebd8a5331c0d1825face034cca10e8b3b535
