Fix typo

Author: artivis

articles/ros2_node_idl/interface_declaration.xml

@@ -19,7 +19,7 @@
         avoid_ros_namespace_conventions="false" />
     </topic>
     <service name="/example_service" type="std_srvs/srv/Empty" client="true" />
-    <action name="/example_action", type="example_interfaces/action/Fibonacci" client="true" />
+    <action name="/example_action" type="example_interfaces/action/Fibonacci" client="true" />
   </node>
 </interface>
 ```