Remove support for IE conditional scripts and styles

Returns false if conditional scripts or styles are identified; updates comments; removes files that were only loaded conditionally.

Author: joedolson

Gruntfile.js

@@ -644,7 +644,6 @@ module.exports = function(grunt) {
 					// Exceptions.
 					'!wp-includes/css/dashicons.css',
 					'!wp-includes/css/wp-embed-template.css',
-					'!wp-includes/css/wp-embed-template-ie.css'
 				]
 			},
 			colors: {