Update app.py

app.py

@@ -108,7 +108,7 @@ async def init():
     
     # Create a chain that uses the Chroma vector store
     chain = ConversationalRetrievalChain.from_llm(
-        ChatOpenAI(temperature=0, model="gpt-3.5-turbo-16k", streaming=True),
+        ChatOpenAI(temperature=0, model="gpt-4", streaming=True),
         chain_type="stuff",
         retriever=docsearch.as_retriever(search_kwargs={'k':5}),
         memory=memory,