Update chatllm.py

fix bug: openai api get result

chatllm.py

@@ -99,7 +99,7 @@ class ChatLLM(LLM):
             }
 
             response = requests.post(OPENAI_URL, headers=headers, json=payload)
-            result = response.choice[0].text
+            result = response.choices[0].text
             
             #  将当次的ai回复内容加入history
             self.history.append((prompt, result))