[css-overflow] Hide tests results by default

Author: frivoal

css-overflow-4/Overview.bs

@@ -29,7 +29,7 @@ url: https://drafts.csswg.org/selectors-3/#subject; type: dfn; text: subject;
 url: https://www.w3.org/TR/CSS21/visudet.html#strut; type: dfn; text: strut;
 </pre>
 <pre class=metadata>
-WPT Display: open
+WPT Display: closed
 WPT Path Prefix: /css/css-overflow/line-clamp/
 </pre>
 	<style>