fix deprecated setting migration

db/migrate/20180508142711_remove_invite_passthrough_hours.rb

@@ -1,5 +1,9 @@
 class RemoveInvitePassthroughHours < ActiveRecord::Migration[5.1]
-  def change
+  def up
     execute "DELETE FROM site_settings WHERE name = 'invite_passthrough_hours'"
   end
+
+  def down
+    raise ActiveRecord::IrreversibleMigration
+  end
 end