jqueryui.com: Restore hiding of list-item bullets in demo navigation

Previously, the background rule implicitly overrode the
background-image to achieve the same effect.

Follows-up a4e2aaa and e535964.

Author: Krinkle

themes/jqueryui.com/style.css

@@ -109,6 +109,10 @@ a,
 	background: #eee;
 }
 
+#content .demo-list li::marker {
+	content: "";
+}
+
 #content .demo-list .active {
 	background: #fff;
 }