Enhance portfolio reset functionality in app.py

- Added deletion of 'display_contest_info' from session state when clearing the portfolio, ensuring a complete reset of relevant data.
- This improvement streamlines user experience by providing a more thorough reset process during portfolio management.

app.py

@@ -181,6 +181,7 @@ with tab1:
         st.info("If you have a portfolio of lineups, you can upload them here to see how they would have performed against the field")
         if st.button('Clear portfolio', key='reset2'):
             st.session_state['portfolio_df'] = None
+            del st.session_state['display_contest_info']
         st.session_state['portfolio_file'] = st.file_uploader("Upload Portfolio File (CSV or Excel)", type=['csv', 'xlsx', 'xls'])
         try:
             st.session_state['portfolio_df'] = pd.read_csv(st.session_state['portfolio_file'])