Revert D27753803: [19/n][torch/elastic][upstream] Replace pytorch.distributed.launch with torchelastic launcher
Test Plan: revert-hammer
Differential Revision:
D27753803 (https://github.com/pytorch/pytorch/commit/7c708ef4ea740972a6cb9a06285772a708f0cc55)
Original commit changeset: 5f24bcfdcb70
fbshipit-source-id: 650e229b788d046450615364e5cba65065a95e3b
