switch default model to be gpt-4

streamlit_app.py

@@ -119,7 +119,7 @@ with st.sidebar:
     st.subheader("Models and parameters")
     selected_model = st.sidebar.selectbox(label="Choose an OpenAI model", 
                                           options=["gpt-3.5-turbo-0125", "gpt-4-0125-preview"], 
-                                          index=0,
+                                          index=1,
                                           key="selected_model")
     temperature = st.sidebar.slider("temperature", min_value=0.0, max_value=2.0, 
                                     value=0.0, step=0.01)