Remove THPPlugin. (#17790)
Summary:
It doesn't seem to be used.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/17790
Reviewed By: ezyang
Differential Revision: D14380897
Pulled By: gchanan
fbshipit-source-id: 3c3884a08c3b6c1489347d439509b19e079c5861
