css3d_youtube.html: Fixed Mixed Content Error (SSL) (#9802)

examples/css3d_youtube.html

@@ -42,7 +42,7 @@
 				iframe.style.width = '480px';
 				iframe.style.height = '360px';
 				iframe.style.border = '0px';
-				iframe.src = [ 'http://www.youtube.com/embed/', id, '?rel=0' ].join( '' );
+				iframe.src = [ 'https://www.youtube.com/embed/', id, '?rel=0' ].join( '' );
 				div.appendChild( iframe );
 
 				var object = new THREE.CSS3DObject( div );