fix typo

nav2_docking/opennav_docking/test/test_docking_server.py

@@ -215,7 +215,7 @@ def test_docking_server(self):
             goal, feedback_callback=self.action_feedback_callback)
         rclpy.spin_until_future_complete(self.node, future)
         self.goal_handle = future.result()
-        assert goal_handle.accepted
+        assert self.goal_handle.accepted
         # future.add_done_callback(self.action_goal_callback)
 
         print('test_docking_server dock start OK')