Make Dropout.__repr__ consistent with other modules (#22110)
Summary:
Fixes https://github.com/pytorch/pytorch/issues/22106.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/22110
Differential Revision: D15958821
Pulled By: ezyang
fbshipit-source-id: 89381dc3bfa79544580e20fea906cef4f5101b61