Add missing use Friendica\DI statement in Util\Emailer

src/Util/Emailer.php

@@ -7,6 +7,7 @@ namespace Friendica\Util;
 use Friendica\Core\Config;
 use Friendica\Core\Hook;
 use Friendica\Core\Logger;
+use Friendica\DI;
 use Friendica\Protocol\Email;
 
 /**