Add empty locale extender to clear cache properly on enable/disable.

See https://github.com/flarum/core/pull/2020#issuecomment-616149583

extensions/suspend/extend.php

@@ -32,6 +32,8 @@ return [
     (new Extend\Model(User::class))
         ->dateAttribute('suspended_until'),
 
+    new Extend\Locales(__DIR__ . '/locale'),
+
     function (Dispatcher $events) {
         $events->subscribe(Listener\AddUserSuspendAttributes::class);
         $events->subscribe(Listener\RevokeAccessFromSuspendedUsers::class);