upgrade getdeps GitHub actions to Ubuntu 20 (#516)
Summary:
link: https://github.com/facebook/fbthrift/pull/516
link: https://github.com/facebook/watchman/pull/1050
link: https://github.com/facebook/proxygen/pull/426
link: https://github.com/facebook/folly/pull/1842
link: https://github.com/facebook/fboss/pull/117
Sadly, even though Ubuntu 18.04 is still in LTS, GitHub is deprecating
its runner image.
Migrate the generated GitHub Actions to 20.04.
https://github.com/actions/runner-images/issues/6002
https://github.blog/changelog/2022-08-09-github-actions-the-ubuntu-18-04-actions-runner-image-is-being-deprecated-and-will-be-removed-by-12-1-22/
Reviewed By: fanzeyi
Differential Revision:
D38877286
fbshipit-source-id:
85f3324d6666eacb190a43985585b438de69d545