Updating submodules
Updating submodules

Summary:
GitHub commits:

https://github.com/facebook/folly/commit/83159cb300d27ebc0489cdfae3c390521b1a8570
https://github.com/facebook/watchman/commit/bc517573cab4b20de84f47b08eb167914df6dd01
https://github.com/facebookexternal/stl_tasks/commit/7956daeeec7e11cc0d73cfaa1950d5bfa7ad24b2
https://github.com/facebookresearch/multimodal/commit/5f3d5b8e837247fc82e2f4412de27f266cfddabb

Reviewed By: yns88

fbshipit-source-id: c206542d859936d5b7a08c184d45de8c13018601

facebookincubator/mvfst,facebookincubator/mvfst,facebookincubator/mvfst,facebookincubator/mvfst,facebookincubator/mvfst