Style FeatureToggle option for easier change

When the list of active features is empty, Rubocop wants the hash braces
to be collapsed to `{}`. While that's easier to read, we would need to
change that every time we add an entry or remove it. Instead I moved the
comment into the hash which satisfies Rubocop and is apt in that place.

This could also ease merge conflict resolution when we work on several
features in parallel.

lib/open_food_network/feature_toggle.rb

@@ -47,10 +47,9 @@ module OpenFoodNetwork
     }.freeze
 
     # Features you would like to be enabled to start with.
-    #
-    # Copy features here that were activated in a migration so that new
-    # instances, development and test environments have the feature active.
     ACTIVE_BY_DEFAULT = {
+      # Copy features here that were activated in a migration so that new
+      # instances, development and test environments have the feature active.
     }.freeze
 
     def self.setup!