Update follow_joint_trajectory.md

Added a note and a preference of the stretch driver

ros2/follow_joint_trajectory.md

@@ -1,8 +1,10 @@
 ## FollowJointTrajectory Commands
 !!! note
     ROS 2 tutorials are still under active development. 
+!!! note 2
+    For this exercise you'll need to have Ubuntu 22.04 and ROS Iron for it to work completly.
 
-Stretch driver offers a [`FollowJointTrajectory`](http://docs.ros.org/en/api/control_msgs/html/action/FollowJointTrajectory.html) action service for its arm. Within this tutorial, we will have a simple FollowJointTrajectory command sent to a Stretch robot to execute.
+Stretch driver offers a [`FollowJointTrajectory`](http://docs.ros.org/en/api/control_msgs/html/action/FollowJointTrajectory.html) action service for its arm. Within this tutorial, we will have a simple FollowJointTrajectory command sent to a Stretch robot to execute. And just as the past practice, it's preferable to have the stretch driver in trajectory mode.
 
 ## Stow Command Example