releases.jquery.com: fix broken powered by img

This hardcoded path works fine on the (old) production server,
but on staging, locally, and on the (new) production server this
is a 404 Not Found.

Reference this in a way that lets WordPress control where this
URL is in actuality. This matches the way other images and stylesheets
are referenced throughout the repo, this was the only case of a
hardcoded path that I could find.

Author: Krinkle

themes/releases.jquery.com/page.php

@@ -38,7 +38,7 @@
 	<div id="content">
 		<?php if ( !count( get_post_meta( $post->ID, "hide_title" ) ) ) : ?>
 		<h1 class="entry-title"><?php the_title(); ?></h1>
-		<div class="powered-by">Powered by <a href="https://www.stackpath.com"><img src="/jquery-wp-content/themes/jquery/images/stackpath.png"></a></div>
+		<div class="powered-by">Powered by <a href="https://www.stackpath.com"><img src="<?php echo get_template_directory_uri(); ?>/images/stackpath.png"></a></div>
 		<hr>
 		<?php endif; ?>