Notify settings listeners of changes to experiments

lib/settings.dart

@@ -112,11 +112,13 @@ class Settings extends ChangeNotifier {
   /// Turn on a specific experiment.
   enableExperiment(String key) {
     experiments.update(key, (value) => true, ifAbsent: () => true);
+    notifyListeners();
   }
 
   /// Turn off a specific experiment
   disableExperiment(String key) {
     experiments.update(key, (value) => false, ifAbsent: () => false);
+    notifyListeners();
   }
 
   /// Construct a default settings object.