Switch davinci for gpt-3.5-turbo-instruct

chain.py

@@ -105,7 +105,7 @@ QUESTION: {question}
 ANSWER:"""
     PROMPT = PromptTemplate(template=template, input_variables=["question", "context"])
     doc_chain = load_qa_chain(
-        OpenAI(temperature=0, model_name="text-davinci-003", max_tokens=-1),
+        OpenAI(temperature=0, model_name="gpt-3.5-turbo-instruct", max_tokens=-1),
         chain_type="stuff",
         prompt=PROMPT,
         document_prompt=EXAMPLE_PROMPT,