[css-ui-4] Change the spec shortname to css-ui-4

Author: frivoal

css-ui-4/Overview.bs

@@ -3,7 +3,7 @@
 <pre class='metadata'>
 ED: http://dev.w3.org/csswg/css-ui-4/
 Previous Version: http://www.w3.org/TR/css3-ui/
-Shortname: css-ui
+Shortname: css-ui-4
 Level: 4
 Group: csswg
 !Issue Tracking: https://wiki.csswg.org/spec/css4-ui#css4-ui-issues-list