Remove on-the-fly adding of feature toggle entries

We now have a new source of truth. You shouldn't use a feature toggle
without adding it to OpenFoodNetwork::FeatureToggle first. All toggles
are added at boot time already.

lib/open_food_network/feature_toggle.rb

@@ -60,9 +60,7 @@ module OpenFoodNetwork
     end
 
     def self.enabled?(feature_name, user = nil)
-      feature = Flipper.feature(feature_name)
-      feature.add unless feature.exist?
-      feature.enabled?(user)
+      Flipper.enabled?(feature_name, user)
     end
 
     def self.disabled?(feature_name, user = nil)

spec/lib/open_food_network/feature_toggle_spec.rb

@@ -13,13 +13,6 @@ module OpenFoodNetwork
         Flipper.enable(:foo)
         expect(FeatureToggle.enabled?(:foo)).to be true
       end
-
-      it "adds features to the database for easy admin in the UI" do
-        feature = Flipper.feature(:sparkling_new)
-
-        expect { FeatureToggle.enabled?(:sparkling_new) }.
-          to change { feature.exist? }.from(false).to(true)
-      end
     end
   end
 end