Changed the state_publihser type to the robot_state_publihser type because it is deprecated.

launch/description.launch

@@ -13,7 +13,7 @@
 
     <node if="$(arg state_pub)"
           pkg="robot_state_publisher"
-          type="state_publisher"
+          type="robot_state_publisher"
           name="state_publisher">
       <param name="tf_prefix" type="string" value="/$(arg ns)"/>
       <param name="publish_frequency" type="double" value="20.0"/>