shard `trunk / linux-bionic-cuda10.2-py3.9-gcc7 / test (slow` to 2 (#81569)
`trunk / linux-bionic-cuda10.2-py3.9-gcc7 / test (slow` currently has an average TTS of 4 hrs and job duration of 3.3 hrs, so I would like to shard it in order to reduce the time.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/81569
Approved by: https://github.com/huydhn
