mobile_base_arm_tutorial: Fix file directory consistency (#362)

some mentioned ~/ws_moveit2/ and some ~/ws_moveit/

Author: TomGrimwood

doc/examples/mobile_base_arm/mobile_base_arm_tutorial.rst

@@ -15,14 +15,14 @@ Installation
 
 Install the dependencies: ::
 
-  cd ~/ws_moveit/src
+  cd ~/ws_moveit2/src
   wget https://raw.githubusercontent.com/PickNikRobotics/stretch_ros/ros2/stretch_ros.repos
   vcs import < stretch_ros.repos
   rosdep install -r --from-paths . --ignore-src --rosdistro {DISTRO} -y
 
 Build the colcon workspace: ::
 
-  cd ~/ws_moveit
+  cd ~/ws_moveit2
   colcon build --event-handlers desktop_notification- status- --cmake-args -DCMAKE_BUILD_TYPE=Release
 
 Source the colcon workspace: ::