Fix keyboard launch topic name

launch/keyboard_teleop.launch

@@ -5,7 +5,7 @@
   <arg name="ns"            default="helena" />
   <arg name="path"          default="$(find iri_teleop_launch)"/>
   <arg name="config_file"   default="$(arg path)/config/keyboard_teleop.yaml" />
-  <arg name="twist_topic"   default="/$(arg ns)/helena/teleop/cmd_vel"/>
+  <arg name="twist_topic"   default="/$(arg ns)/teleop/cmd_vel"/>
   <arg name="output"        default="screen" />
   <arg name="launch_prefix" default="" />