Remove GitHub Actions CI
Remove GitHub Actions CI

Why: This seems to be causing 500 errors for @pradyunsg on PRs.

https://twitter.com/AndersKaseorg/status/1179851971433385984

xavfernandez/pip,sbidoul/pip,sbidoul/pip,pfmoore/pip,pypa/pip,pradyunsg/pip,rouge8/pip,pfmoore/pip,xavfernandez/pip,xavfernandez/pip,pradyunsg/pip,rouge8/pip,rouge8/pip,pypa/pip