automation: upgrade packages in Linux environment
It's been a while since we've ran pip-compile -U. Let's do that.
When I ran this command, black was upgraded and newer versions of
black complains about formatting differences. I didn't feel like
shaving a yak, so I pinned the current black version to avoid
I manually ran tests against all major Python versions and I'm fairly
certain no new test failures were introduced.
Differential Revision: https://phab.mercurial-scm.org/D9188