4bf4fb9a introduced a bug when including `wpcom-colors.php` by using the
editor. It was missing a directory separate and so it fataled with an
error message like:
`PHP Fatal error: Uncaught Error: Failed opening required '/xxx/seedlet/incwpcom-colors.php' (include_path='.') in /xxx/seedlet/inc/wpcom-editor-colors.php:3