reference minified tinymce file directly

I don't really understand why they've made this change, and even more strangely, it's not reflected in the [trac browser](https://core.trac.wordpress.org/browser/trunk#src/wp-includes/js/tinymce) even though when you pull from SVN the non-minified file has been removed.

I'm going to give a patch to VIP on a zendesk ticket along with asking about the change, let's hold off on merging this until we hear from them maybe?