Update ControllerFlow_ExtLib.yaml

ControllerFlow_ExtLib.yaml

@@ -84,6 +84,8 @@ system_message_prompt_template:
             3.4 Call `update_plan` with the plan you just generated.
           4. Proceed to the next step of the plan, go back to workflow 1.
           5. When every step of the plan is done, call the `finish` command, with a summary of what functions are written and saved.
+
+          **You MUST call `update_plan` whenever you realize one step of the plan is done.**
             
           ### Beginning of an example execution: ###
           Plan: 1. Write a function that fetches weather data from google; 2. Write a function that prints the weather data in a formatted way.