nixos/hardware.nitrokey: update documentation

      type = lib.types.bool;

      default = false;

      description = ''

        Enables udev rules for Nitrokey devices. By default grants access

        to users in the "nitrokey" group. You may want to install the

        nitrokey-app package, depending on your device and needs.

        Enables udev rules for Nitrokey devices.

      '';

    };

  };