remove outdated argument (#1373)
Summary:
The outdated `--flops` argument is not removed.
Pull Request resolved: https://github.com/pytorch/benchmark/pull/1373
Reviewed By: davidberard98
Differential Revision: D42681454
Pulled By: xuzhao9
fbshipit-source-id: f9e7b71b7b5eaf58ac4015b23a906652f5431bc4
