[css-backgrounds] Fix broken link

Author: fantasai

css-backgrounds/Overview.src.html

@@ -19,7 +19,7 @@
   <link rel="stylesheet" type="text/css"
   href="https://www.w3.org/StyleSheets/TR/W3C-WD.css">
   <script defer="defer"
-  src="images/https://test.csswg.org/harness/annotate.js#css-backgrounds-3_dev"
+  src="https://test.csswg.org/harness/annotate.js#css-backgrounds-3_dev"
   type="text/javascript"></script>
 </head>