Fix axis_mappings in the joy_teleop_example.yaml for TwistStamped type

[cosmicog]

The interface_type in the joy_teleop_example.yaml was changed to TwistStamped from Twist in the past.

However, if the parameters under axis_mappings left unchanged, this example config would not work.

I didn't initially pay attention to the config file and got:

...
[joy_teleop-8] AttributeError: 'TwistStamped' object has no attribute 'angular'
[ERROR] [joy_teleop-8]: process has died
...

Then, changed the values like this;

/**/joy_teleop:
 ros__parameters:
   move:
     type: topic
     interface_type: geometry_msgs/msg/TwistStamped
     topic_name: input_joy/cmd_vel # will publish messages to this
     deadman_buttons: [3] # hold the Y button of F710 to control robot, for safety
     # deadman_axes_negative: [5] # wait for PR #94 to be merged and use this with RT trigger instead
     axis_mappings:
       twist-linear-x: # <----------  [ from linear-x ]
         axis: 1 # left stick for driving forward/backward
         scale: 1.0
         offset: 0
       twist-angular-z: # <---------  [ from angular-z ]
         axis: 3 # right stick for turning
         scale: 0.5
         offset: 0
       header-frame_id:
         value: 'base_link'

Now it works.