Don't clear class for audio/video when removing xss - refs BT#14026

Author: AngelFQC

main/inc/lib/formvalidator/Rule/allowed_tags.inc.php

@@ -315,6 +315,7 @@
 $allowed_tags_student['video']['src'] = [];
 $allowed_tags_student['video']['controls'] = [];
 $allowed_tags_student['video']['id'] = [];
+$allowed_tags_student['video']['class'] = [];
 
 $allowed_tags_student['audio'] = [];
 $allowed_tags_student['audio']['autoplay'] = [];
@@ -324,6 +325,7 @@
 $allowed_tags_student['audio']['controls'] = [];
 $allowed_tags_student['audio']['muted'] = [];
 $allowed_tags_student['audio']['id'] = [];
+$allowed_tags_student['audio']['class'] = [];
 
 $allowed_tags_student['source'] = [];
 $allowed_tags_student['source']['type'] = [];