[css-transitions-2] Drop level suffix from Shortname

Author: birtles

css-transitions-2/Overview.bs

@@ -20,7 +20,7 @@
 Title: CSS Transitions Level 2
 Status: ED
 Work Status: Exploring
-Shortname: css-transitions-2
+Shortname: css-transitions
 Level: 2
 Group: csswg
 ED: https://drafts.csswg.org/css-transitions-2/