add python dispatch test back to CI and fix typo in test (#69565)
Summary:
The error message was changed following a PR comment. And since the test doesn't run on CI, I forgot to update the test to catch the new error message.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/69565
Reviewed By: mrshenli
Differential Revision: D32932982
Pulled By: albanD
fbshipit-source-id: a1da72b0ca735e72b481bc944039233094f1c422
