Update the scribe category (#1120)
Summary:
We are using the new scribe category `perfpipe_pytorch_user_benchmarks` to upload userbenchmark results to scribe.
Pull Request resolved: https://github.com/pytorch/benchmark/pull/1120
Differential Revision: D38793392
Pulled By: xuzhao9
fbshipit-source-id: 178cf66aa2d4ea3256457edb61863641f4b17b6d
