Update Setting-Up-Simulation-Webots-Advanced.rst (ros2#4146)

The import statement `from launch_ros.actions import Node` was missing in line 3

Signed-off-by: Michael Razum <[email protected]>

source/Tutorials/Advanced/Simulators/Webots/Setting-Up-Simulation-Webots-Advanced.rst

@@ -151,11 +151,10 @@ You have to modify these two other files to launch your new node.
             :language: cmake
 
 
-Go to the file ``robot_launch.py`` and replace ``def generate_launch_description():`` with:
+Go to the file ``robot_launch.py`` and replace it with:
 
 .. literalinclude:: Code/robot_launch_sensor.py
     :language: python
-    :lines: 10-40
 
 This will create an ``obstacle_avoider`` node that will be included in the ``LaunchDescription``.