Missed use

fix missing use statement

src/Content/Text/HTML.php

@@ -11,6 +11,7 @@ use Friendica\Core\Addon;
 use Friendica\Core\L10n;
 use Friendica\Core\Config;
 use Friendica\Core\PConfig;
+use Friendica\Core\Protocol;
 use Friendica\Core\Renderer;
 use Friendica\Database\DBA;
 use Friendica\Model\Contact;