update example in classification losses (#69816)
Summary:
Just updated a few examples that were either failing or raising deprecated warnings.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/69816
Reviewed By: bdhirsh
Differential Revision: D33217585
Pulled By: albanD
fbshipit-source-id: c6804909be74585c8471b8166b69e6693ad62ca7
