fix return format

NLP_model/chatbot.py

@@ -110,7 +110,7 @@ You have to use core knowledge and conversation history to chat with users, who
 
 Return Format:
 Respond in friendly, natural, concise and use only English like a real tour guide. 
-Return in Markdown format that telegram can read
+Return in HTML format that telegram can read.
 
 Warning:
 Let's support users like a real tour guide, not a bot. The information in core knowledge is your own knowledge.