SimplePie faster regex for sanitizing URLs

Can simplify the regex (faster because anchored) for cleaning URLs based
on the fact that we only have to deal with HTTP or HTTPS
https://github.com/FreshRSS/FreshRSS/pull/715

lib/SimplePie/SimplePie/Misc.php

@@ -2248,7 +2248,7 @@ function embed_wmedia(width, height, link) {
 	 */
 	function url_remove_credentials($url)	//FreshRSS
 	{
-		return preg_replace('#(?<=//)[^/:@]+:[^/:@]+@#', '', $url);
+		return preg_replace('#^(https?://)[^/:@]+:[^/:@]+@#i', '$1', $url);
 	}
 }