Upgrade to NixOS 22.11

I was wondering why our trusty nixpkgs upgrade bot stopped sending MRs with new nixpkgs versions so we'd get security updates.

Seems because the NixOS channel we were using, 21.11, reached EOL a while ago!

The next channel, 22.05, also reached EOL: https://status.nixos.org/

To be getting security updates we need to upgrade to 22.11.

This MR is about that.

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Fixes #126 (closed). Fixes #141 (closed).