pythonPackages.github-cli: removed

[andir]

Motivation for this change

since upstream declared the project non-functional there isn't much use for this package anymore. re-adding it would be trivial.

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IMPORTANT: github-cli does not function anymore since API v2 has been
replaced by API v3 A possible alternative for github-cli that addresses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

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

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option build-use-sandbox in nix.conf on non-NixOS)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nox --run "nox-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Fits CONTRIBUTING.md.

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