[css-color-4] Remove 'prepare for tr' metadata.

Author: tabatkins

css-color-4/Overview.bs

@@ -1,7 +1,6 @@
 <pre class=metadata>
 Title: CSS Color Module Level 4
 Status: ED
-Prepare for TR: true
 Work Status: Exploring
 ED: https://drafts.csswg.org/css-color/
 TR: https://www.w3.org/TR/css-color-4/