Twenty Fifteen: Proper Escaping Missing From HTML5 Shiv Header Call

[philiparthurmoore]

This:

	<!--[if lt IE 9]>
	<script src="<?php echo get_template_directory_uri(); ?>/js/html5.js"></script>
	<![endif]-->

Should be this:

	<!--[if lt IE 9]>
	<script src="<?php echo esc_url( get_template_directory_uri() ); ?>/js/html5.js"></script>
	<![endif]-->

[iandstewart]

In 30218:

Twenty Fifteen: escaping for the HTML5 shiv call.

Props philiparthurmoore, fixes #30212