add :nodoc: to AM::AttributeMethods::AttributeMethodMatcher [ci skip]

activemodel/lib/active_model/attribute_methods.rb

@@ -314,7 +314,7 @@ def define_proxy_call(include_private, mod, name, send, *extra) #:nodoc:
           RUBY
         end
 
-        class AttributeMethodMatcher
+        class AttributeMethodMatcher #:nodoc:
           attr_reader :prefix, :suffix, :method_missing_target
 
           AttributeMethodMatch = Struct.new(:target, :attr_name, :method_name)