Improving docs for MultiLabelSoftMarginLoss (#16644)
Summary:
Resolves #15863
Changed the documentation for MultiLabelSoftMarginLoss and MultiLabelMarginLoss to be more explicit about the `target` format.
More than happy to change the messaging based on discussion.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/16644
Differential Revision: D13912395
Pulled By: soumith
fbshipit-source-id: 24a3c214c5f6f9d043e25b13ac758c1c1211b641
