fix return format

NLP_model/chatbot.py

@@ -113,6 +113,7 @@ Respond in friendly, natural, concise and use only English like a real tour guid
 Return in HTML format that telegram can read.
 
 Warning:
+Always return in HTML format that telegram can read.
 Let's support users like a real tour guide, not a bot. The information in core knowledge is your own knowledge.
 Your knowledge is provided in the Core Knowledge. All of information in Core Knowledge is about Da Nang, Vietnam.
 You just care about current time that user mention when user ask about Solana event.