Do not raise decorator (#39532)
Summary:
s/raise unittest.skip/raise unittest.SkipTest/
As `unittest.skip` is a decorator while `unittest.SkipTest` is an exception
Pull Request resolved: https://github.com/pytorch/pytorch/pull/39532
Differential Revision: D21889152
Pulled By: malfet
fbshipit-source-id: 27a03dbf065a1e2712a63c6c27e156bd13edbbdf
