refactor: 优化导出日志的时间格式

--bug=1048109 --user=王孝刚 【应用】对话日志导出后，提问时间格式显示问题 https://www.tapd.cn/57709429/s/1598300

Author: wxg0103

apps/application/serializers/chat_serializers.py

@@ -189,7 +189,8 @@ def to_row(row: Dict):
                         f"{improve_paragraph_list[index].get('title')}\n{improve_paragraph_list[index].get('content')}"
                         for index in range(len(improve_paragraph_list))]),
                     row.get('message_tokens') + row.get('answer_tokens'), row.get('run_time'),
-                    str(row.get('create_time'))]
+                    str(row.get('create_time').strftime('%Y-%m-%d %H:%M:%S')
+                        )]
 
         def export(self, data, with_valid=True):
             if with_valid: