pythonPackages.github-cli: removed since upstream declared project non-functional

also does not work on python3 even thought we provide it there…

Note on the upstream repo [1]:
> IMPORTANT: github-cli does not function anymore since API v2 has been
> replaced by API v3 A possible alternative for github-cli that addresses
> API v3 is Stephen Celis' [ghi](https://github.com/stephencelis/ghi)

[1] https://github.com/jsmits/github-cli