Update app.py

app.py

@@ -3,7 +3,7 @@ from transformers import AutoModelForCausalLM, AutoTokenizer
 import torch
 
 class VietnameseChatbot:
-    def __init__(self, model_name="vinai/gpt-neo-1.3B-vietnamese-news"):
+    def __init__(self, model_name="vinai/PhoGPT-4B-Chat"):
         """
         Initialize the Vietnamese chatbot with a pre-trained model
         """