Make _protected_ivars private

This method is only used internally and it being public it was being
retorned in the `action_methods` list.

actionmailer/lib/action_mailer/base.rb

@@ -455,10 +455,6 @@ class Base < AbstractController::Base
 
     PROTECTED_IVARS = AbstractController::Rendering::DEFAULT_PROTECTED_INSTANCE_VARIABLES + [:@_action_has_layout]
 
-    def _protected_ivars # :nodoc:
-      PROTECTED_IVARS
-    end
-
     helper ActionMailer::MailHelper
 
     class_attribute :delivery_job, default: ::ActionMailer::DeliveryJob
@@ -1030,6 +1026,10 @@ def instrument_name
         "action_mailer"
       end
 
+      def _protected_ivars
+        PROTECTED_IVARS
+      end
+
       ActiveSupport.run_load_hooks(:action_mailer, self)
   end
 end

actionpack/lib/abstract_controller/rendering.rb

@@ -120,7 +120,7 @@ def _normalize_render(*args, &block) # :nodoc:
       options
     end
 
-    def _protected_ivars # :nodoc:
+    def _protected_ivars
       DEFAULT_PROTECTED_INSTANCE_VARIABLES
     end
   end

actionpack/lib/action_controller/base.rb

@@ -263,9 +263,10 @@ def self.without_modules(*modules)
       @_view_renderer @_lookup_context @_routes @_view_runtime @_db_runtime @_helper_proxy
     )
 
-    def _protected_ivars # :nodoc:
+    def _protected_ivars
       PROTECTED_IVARS
     end
+    private :_protected_ivars
 
     ActiveSupport.run_load_hooks(:action_controller_base, self)
     ActiveSupport.run_load_hooks(:action_controller, self)