Motivation for this change

tasknc has been broken for some reason for as long as I can remember, segfaulting at the start. man pages were not available either.

This commit updates tasknc to the most recent version which contains some fixes. Made the manpages work (also removes the makefile hack). Cleaned up dependencies (fixed the taskwarrior dependency, it's a runtime one. Also some nativeBuildInputs stuff). Apparently tasknc changed owners, so I got that changed too.

Ping @matthiasbeyer

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.