Fix docstring for nn.Hardsigmoid (#70987)
Summary:
Fixes nn.Hardsigmoid's docstring problem reported at https://github.com/pytorch/pytorch/issues/70498.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/70987
Reviewed By: dagitses
Differential Revision: D33476974
Pulled By: albanD
fbshipit-source-id: bf3a1c485dd2c369c56981f9afbfe45aa9cee2cc