Correct loss docstrings (#17300)
Summary:
In the loss doc description, replace the deprecated 'reduct' and 'size_average' parameters with the 'reduction' parameter.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/17300
Differential Revision: D14195789
Pulled By: soumith
fbshipit-source-id: 625e650ec20f13b2d22153a4a535656cf9c8f0eb
