remove signing from server

def cmd_signing_remove(self, args):
        '''remove signing from server'''
        if not self.master.mavlink20():
            print("You must be using MAVLink2 for signing")
            return
        self.master.mav.setup_signing_send(self.target_system, self.target_component, [0]*32, 0)
        self.master.disable_signing()
        print("Removed signing")