[css-animations-1] Update affiliation for Brian Birtles

Author: birtles

css-animations-1/Overview.bs

@@ -27,7 +27,7 @@ Previous Version: https://www.w3.org/TR/2012/WD-css3-animations-20120403/
 Editor: Dean Jackson, Apple Inc., dino@apple.com, w3cid 42080
 Editor: L. David Baron, Mozilla https://www.mozilla.org/, https://dbaron.org/, w3cid 15393
 Editor: Tab Atkins Jr., Google, http://xanthir.com/contact/, w3cid 42199
-Editor: Brian Birtles, Mozilla, bbirtles@mozilla.com, w3cid 43194
+Editor: Brian Birtles, Invited Expert, brian@birchill.co.jp, w3cid 43194
 Former Editor: David Hyatt, Apple Inc.
 Former Editor: Chris Marrin, Apple Inc.
 Former Editor: Sylvain Galineau, Adobe, galineau@adobe.com