remove requried attribute in xml launch file

[marcoag]

Signed-off-by: Marco A. Gutierrez marco@openrobotics.org

Bug fix

Fixed bug

Airport launch file throws an error when trying to run the demo:

...
launch.invalid_launch_file_error.InvalidLaunchFileError: Caught exception when trying to load file of format [xml]: Unexpected attribute(s) found in `node`: {'required'}

Even though the required attribute is supported for nodes on python launch files, based on the error above and the documentation found here: https://design.ros2.org/articles/roslaunch_xml.html it seems that it is not available on for xml launch files.

I believe we are only getting this error now on galactic due to the changes introduced here: ros2/launch#468.

Fix applied

required attribute has been removed from launch file.

[youliangtan]

Thx for fixing this!