[css-backgrounds-3] Shift Bert to Former Editor since he's no longer in the WG :(

Author: fantasai

css-backgrounds-3/Overview.bs

@@ -11,7 +11,7 @@ TR: https://www.w3.org/TR/css-backgrounds-3/
 Previous Version: https://www.w3.org/TR/2020/CR-css-backgrounds-3-20201222/
 Previous Version: https://www.w3.org/TR/2017/CR-css-backgrounds-3-20171017/
 Previous version: https://www.w3.org/TR/2014/CR-css3-background-20140909/
-Editor: Bert Bos, W3C, bert@w3.org, w3cid 3343
+Former Editor: Bert Bos, W3C, bert@w3.org, w3cid 3343
 Editor: Elika J. Etemad / fantasai, Apple, http://fantasai.inkedblade.net/contact, w3cid 35400
 Editor: Brad Kemper, Invited Expert, brad.kemper@gmail.com, w3cid 43245
 Abstract: This draft contains the features of CSS relating to borders and backgrounds. The main extensions compared to <a href="https://www.w3.org/TR/CSS2/">level&nbsp;2</a> are borders consisting of images, boxes with multiple backgrounds, boxes with rounded corners and boxes with shadows.