Fixed the 'Theme URI' of loudness to point to the correct location (#6708)

loudness/style.css

@@ -1,6 +1,6 @@
 /*
 Theme Name: Loudness
-Theme URI: https://wordpress.com/loudness
+Theme URI: https://loudnessthemedemo.wordpress.com/
 Author: Automattic
 Author URI: https://automattic.com
 Description: A bold opinionated theme for music and learning