Move Mantaroh to former editors

Author: birtles

Overview.bs

@@ -10,9 +10,9 @@ Abstract: Defines an API and markup for creating animations that are either
           triggered by or tied to the scroll offset of a scroll container.
 Editor: Brian Birtles <bbirtles@mozilla.com>
 Editor: Botond Ballo <botond@mozilla.com>
-Editor: Mantaroh Yoshinaga <mantaroh@mozilla.com>
 Editor: Stephen McGruer <smcgruer@google.com>
 Editor: Antoine Quint <graouts@apple.com>
+Former editor: Mantaroh Yoshinaga
 !Issue Tracking: <a href="https://github.com/WICG/scroll-animations/issues">GitHub Issues</a>
 </pre>
 <pre class=anchors>