Update Nixpkgs to something less ancient

[Atemu]

Currently, robotnix still uses 21.11:

https://github.com/nix-community/robotnix/blob/73d6b0b142e3f2844e6caaf820e8be3bd8cde2c6/flake.nix#L5

We should update that to at least 22.11 which is the last release with python2 which is still used in quite a few places here.

[ajs124]

which is the last release with python2

python2 still exists on nixpkgs master and has been updated quite recently https://github.com/NixOS/nixpkgs/pull/256132.

It's just been marked as insecure, because it's EOL upstream for some years now, but it's still getting (3rd party) updates, so IMHO this shouldn't hold us back from using a nixpkgs newer than 22.11.

[Atemu]

My WIP for reference: https://github.com/nix-community/robotnix/pull/220