Update to drupal 8.0.0-rc1. For more information, see https://www.drupal.org/node/2582663

core/modules/system/templates/indentation.html.twig

@@ -11,10 +11,4 @@
  * @ingroup themeable
  */
 #}
-<!--
-THIS FILE IS NOT USED AND IS HERE AS A STARTING POINT FOR CUSTOMIZATION ONLY.
-See https://api.drupal.org/api/function/theme_indentation/8 for details.
-After copying this file to your theme's folder and customizing it, remove this
-HTML comment.
--->
 {% for i in 1..size if size > 0 %}<div class="js-indentation indentation">&nbsp;</div>{% endfor %}