Update biblio.ref: css-backgrounds-4 and css-page-template-1

This update adjusts the URLs of the entries for CSS Backgrounds and Borders
Module Level 4 and CSS Pagination Templates Module Level 3, so that they target
the final document directly.

Author: tidoust

biblio.ref

@@ -879,8 +879,8 @@
 %T CSS Pagination Templates Module Level 3
 %A Alan Stearns
 %S Proposal for a CSS module
-%O (Retrieved 4 April 2012)
-%U https://drafts.csswg.org/css3-page-template/
+%O (Retrieved 11 June 2020)
+%U https://drafts.csswg.org/css-page-template-1/
 
 %L CSS3-POSITIONING
 %T CSS Positioned Layout Module Level 3
@@ -1206,11 +1206,12 @@
 
 %L CSS4BACKGROUND
 %T CSS Backgrounds and Borders Module Level 4
+%A Bert Bos
 %A Elika J. Etemad
-%A Håkon Wium Lie
+%A Lea Verou
 %S Proposal for a CSS module
-%O (Retrieved 2 June 2010)
-%U https://drafts.csswg.org/css4-background/
+%O (Retrieved 11 June 2020)
+%U https://drafts.csswg.org/css-backgrounds-4/
 
 %L CSSBEIJING
 %T Cascading Style Sheets (CSS) Snapshot 2007