Update agent.py

agent.py

@@ -48,8 +48,7 @@ thought: you should always think about what to do next, but use your SEARCH tool
 action: the action to take (should be one of [UPDATE-TASK, SEARCH, COMPLETE]) action_input=XXX
 observation: the result of the action
 thought: you can find more information on the internet, try using a search engine
-
-... (thought/action/observation/thought can repeat 0 times)
+... (thought/action/observation/thought can repeat 0 times, and must end with action)
 
 You are attempting to complete the task
 task: {task}