Don't require slow test reporting in `run_tests.py --pytest` (#24448)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/24448
The setting `--durations=10` was hard-coded, which is annoying as I
don't necessarily care. A good alternative to get the same behavior is:
```
python run_tests.py --pytest -- --durations=10
```
Test Plan: Imported from OSS
Differential Revision: D16876380
Pulled By: suo
fbshipit-source-id: 1e14d366db45b6b9bf4a4ab1633b0f6ece29f6bc
