[css-text-decor-4] Fix metadata so that the spec generates properly

Author: frivoal

css-text-decor-4/Overview.bs

@@ -4,7 +4,6 @@ Shortname: css-text-decor
 Level: 4
 Status: ED
 Date: 2018-03-13
-Prepare for TR: true
 Work Status: Exploring
 Group: csswg
 ED: https://drafts.csswg.org/css-text-decor-4/