Avoid double super call in some cases.

If super was false earlier, it is still going to be false, so we don't
need to call it again at the end of the method.

activemodel/lib/active_model/attribute_methods.rb

@@ -431,15 +431,14 @@ def method_missing(method, *args, &block)
     alias :respond_to_without_attributes? :respond_to?
     def respond_to?(method, include_private_methods = false)
       if super
-        return true
+        true
       elsif !include_private_methods && super(method, true)
         # If we're here then we haven't found among non-private methods
         # but found among all methods. Which means that the given method is private.
-        return false
-      elsif match_attribute_method?(method.to_s)
-        return true
+        false
+      else
+        !match_attribute_method?(method.to_s).nil?
       end
-      super
     end
 
     protected