[web-animations] Update editors list

As resolved here:

  https://logs.csswg.org/irc.w3.org/fx/2018-07-02/#e1042740

Thanks Shane and Doug for all your help!

Author: birtles

web-animations-1/Overview.bs

@@ -86,8 +86,10 @@ Repository: w3c/csswg-drafts
 !Tests: <a href="https://github.com/web-platform-tests/wpt/tree/master/web-animations">web-platform-tests web-animations/</a> (<a href="https://github.com/web-platform-tests/wpt/labels/web-animations">ongoing work</a>)
 
 Editor: Brian Birtles 43194, Mozilla, bbirtles@mozilla.com
-Editor: Shane Stephens 47691, Google Inc, shans@google.com
-Editor: Douglas Stockwell, Google Inc, dstockwell@google.com
+Editor: Robert Flack 98451, Google Inc, flackr@google.com
+Editor: Antoine Quint 51377, Apple Inc, graouts@apple.com
+Former Editor: Shane Stephens 47691, Google Inc, shans@google.com
+Former Editor: Douglas Stockwell, Google Inc, dstockwell@google.com
 Former Editor: Alex Danilo 31960, Google Inc, adanilo@google.com
 Former Editor: Tab Atkins 42199, Google Inc, jackalmage@gmail.com
 Abstract: This specification defines a model for synchronization and