Trying to fix mermaid diagram for readthedocs.

Author: Murilo Marinho

docs/source/action_clients.rst

@@ -18,14 +18,14 @@ this complexity in consideration when designing your packages to make sure that
 .. mermaid::
 
     %%{init: { "theme" : "dark" }}%%
-    sequenceDiagram;
-    Action Client->>+Action Server: action_client.send_goal_async()
-    Action Server-->>-Action Client: ActionClientNode.goal_response_callback()
-    Action Client->>+Action Server: action_client.get_result_async()
-        loop While action has not ended
-        Action Server-->>Action Client: ActionClientNode.action_feedback_callback()
-    end
-    Action Server-->>-Action Client: ActionClientNode.action_result_callback()
+    sequenceDiagram
+        Action Client->>+Action Server: action_client.send_goal_async()
+        Action Server-->>-Action Client: ActionClientNode.goal_response_callback()
+        Action Client->>+Action Server: action_client.get_result_async()
+            loop While action has not ended
+            Action Server-->>Action Client: ActionClientNode.action_feedback_callback()
+        end
+        Action Server-->>-Action Client: ActionClientNode.action_result_callback()
 
 #. Create the Node with an :code:`ActionClient`.
 #. Update the :file:`setup.py` so that :program:`ros2 run` finds the node (if needed).