update ActiveModel::ObserverArray documentation [ci skip]

activemodel/lib/active_model/observer_array.rb

@@ -5,13 +5,14 @@ module ActiveModel
   # a particular model class.
   class ObserverArray < Array
     attr_reader :model_class
-    def initialize(model_class, *args)
+    def initialize(model_class, *args) #:nodoc:
       @model_class = model_class
       super(*args)
     end
 
-    # Returns true if the given observer is disabled for the model class.
-    def disabled_for?(observer)
+    # Returns +true+ if the given observer is disabled for the model class,
+    # +false+ otherwise.
+    def disabled_for?(observer) #:nodoc:
       disabled_observers.include?(observer.class)
     end