Fix method visibility in ActiveRecord::Attributes

Follow-up to rails#44666.

`ActiveRecord::ModelSchema#reload_schema_from_cache` is protected and
`ActiveModel::AttributeRegistration#reset_default_attributes` is
private, so their overrides in `ActiveRecord::Attributes` should match
those visibilities.

Author: jonathanhefner

activerecord/lib/active_record/attributes.rb

@@ -249,12 +249,11 @@ def _default_attributes # :nodoc:
         end
       end
 
-      def reload_schema_from_cache(*)
-        reset_default_attributes!
-        super
-      end
-
-      alias :reset_default_attributes :reload_schema_from_cache
+      protected
+        def reload_schema_from_cache(*)
+          reset_default_attributes!
+          super
+        end
 
       private
         NO_DEFAULT_PROVIDED = Object.new # :nodoc:
@@ -276,6 +275,10 @@ def define_default_attribute(name, value, type, from_user:)
           _default_attributes[name] = default_attribute
         end
 
+        def reset_default_attributes
+          reload_schema_from_cache
+        end
+
         def resolve_type_name(name, **options)
           Type.lookup(name, **options, adapter: Type.adapter_name_from(self))
         end