Mark Tails 3.9~rc1 as released.

debian/changelog

-tails (3.9~rc1) UNRELEASED; urgency=medium
+tails (3.9~rc1) unstable; urgency=medium
 
   * Major changes
     - Integrate the Additional Software Packages feature into the desktop
@@ -133,7 +133,7 @@ tails (3.9~rc1) UNRELEASED; urgency=medium
     - Take into account that apt(8) won't return when run in the remote shell
       with the ASP hooks enabled.
 
- -- Tails developers <tails@boum.org>  Thu, 16 Aug 2018 13:46:22 +0000
+ -- Tails developers <tails@boum.org>  Thu, 16 Aug 2018 18:37:47 +0000
 
 tails (3.8) unstable; urgency=medium