question classifier prompt optimization (#3479)

api/core/workflow/nodes/question_classifier/question_classifier_node.py

         model_mode = ModelMode.value_of(node_data.model.mode)
         classes = node_data.classes
         class_names = [class_.name for class_ in classes]
-        class_names_str = ','.join(class_names)
+        class_names_str = ','.join(f'"{name}"' for name in class_names)
         instruction = node_data.instruction if node_data.instruction else ''
         input_text = query
         memory_str = ''

api/core/workflow/nodes/question_classifier/template_prompts.py

 
 QUESTION_CLASSIFIER_ASSISTANT_PROMPT_2 = """
     {"keywords": ["bad service", "slow", "food", "tip", "terrible", "waitresses"],
-    "categories": ["Experience""]}```
+    "categories": ["Experience"]}```
 """
 
 QUESTION_CLASSIFIER_USER_PROMPT_3 = """