Fix test after JSB got fixed (#620)

(cherry picked from commit b7b3844)

Author: christophfroehlich

example_13/test/test_three_robots_launch.py

@@ -329,9 +329,7 @@ def test_behavior(self, proc_output):
             "/joint_states",
             [
                 "rrbot_with_sensor_joint1",
-                "rrbot_joint1",
                 "rrbot_with_sensor_joint2",
-                "rrbot_joint2",
                 "threedofbot_joint1",
                 "threedofbot_joint2",
                 "threedofbot_joint3",