[css-content] change publication date

Author: dauwhe

css-content/Overview.bs

@@ -1,7 +1,7 @@
 <h1>CSS Generated Content Module Level 3</h1>
 <pre class='metadata'>
 Status: WD
-Date: 2016-05-24
+Date: 2016-05-31
 Work Status: Exploring
 Shortname: css-content
 Level: 3