Update diff_drive_example.launch.py (#207) (#209)

(cherry picked from commit e20382a)

Co-authored-by: Jakub Delicat <[email protected]>

gz_ros2_control_demos/launch/diff_drive_example.launch.py

@@ -67,7 +67,7 @@ def generate_launch_description():
         output='screen'
     )
 
-    load_joint_trajectory_controller = ExecuteProcess(
+    load_diff_drive_controller = ExecuteProcess(
         cmd=['ros2', 'control', 'load_controller', '--set-state', 'active',
              'diff_drive_base_controller'],
         output='screen'
@@ -98,7 +98,7 @@ def generate_launch_description():
         RegisterEventHandler(
             event_handler=OnProcessExit(
                 target_action=load_joint_state_controller,
-                on_exit=[load_joint_trajectory_controller],
+                on_exit=[load_diff_drive_controller],
             )
         ),
         node_robot_state_publisher,