cups-pk-helper: init at 0.2.5

Adding this package to environment.systemPackages stops the
"Add new printer" button in gnome-control-center from being grayed out
and stops it from printing:

  (gnome-control-center:16664): printers-cc-panel-WARNING **: Your system does not have the cups-pk-helper's policy "org.opensuse.cupspkhelper.mechanism.all-edit" installed. Please check your installation

But completing the printer setup requires some additional packaging
work. This is what happens when trying to _add_ a printer:

  (gnome-control-center:18733): printers-cc-panel-WARNING **: GDBus.Error:org.freedesktop.DBus.Error.ServiceUnknown: The name org.fedoraproject.Config.Printing was not provided by any .service files
  (gnome-control-center:18733): printers-cc-panel-WARNING **: GDBus.Error:org.freedesktop.DBus.Error.ServiceUnknown: The name org.freedesktop.PackageKit was not provided by any .service files