Update app.py

app.py

@@ -811,7 +811,7 @@ update_functions = {
     'spite': update_plots_spite,
     'trust': update_plots_trust,
     'reciprocity': update_plots_reciprocity,
-    'freeriding': update_plots_freeriding,
+    'free-riding': update_plots_freeriding,
     'cooperation': update_plots_cooperation
 }