[css-text-4] Update "Previous Version"

Author: frivoal

css-text-4/Overview.bs

@@ -7,7 +7,7 @@ Work Status: Exploring
 Group: csswg
 ED: https://drafts.csswg.org/css-text-4/
 TR: https://www.w3.org/TR/css-text-4/
-Previous Version: https://www.w3.org/TR/2015/WD-css-text-4-20150922/
+Previous Version: https://www.w3.org/TR/2019/WD-css-text-4-20191113/
 Editor: Elika J. Etemad / fantasai, Invited Expert, http://fantasai.inkedblade.net/contact, w3cid 35400
 Editor: Koji Ishii, Google, kojiishi@gmail.com, w3cid 45369
 Editor: Alan Stearns, Adobe Systems, stearns@adobe.com, w3cid 46659