Remove plasmashell protocol leftovers
We've switched to the layer shell protocol, thus we don't need the plasma shell protocol anymore in the greeter.
Found while looking how to port kscreenlocker away from kwayland::server.
We've switched to the layer shell protocol, thus we don't need the plasma shell protocol anymore in the greeter.
Found while looking how to port kscreenlocker away from kwayland::server.