[css-ui-3][editorial] Updated/fixed ED and TR URLs

Author: SebastianZ

css-ui-3/Overview.bs

@@ -1,7 +1,7 @@
 <pre class='metadata'>
 Title: CSS Basic User Interface Module Level 3 (CSS3 UI)
-ED: https://drafts.csswg.org/css-ui/
-TR: https://www.w3.org/TR/css3-ui/
+ED: https://drafts.csswg.org/css-ui-3/
+TR: https://www.w3.org/TR/css-ui-3/
 Previous Version: https://www.w3.org/TR/2017/PR-css-ui-3-20171214/
 Shortname: css-ui
 Level: 3