Mark Tails 3.0~beta4 as released.

debian/changelog

-tails (3.0~beta4) UNRELEASED; urgency=medium
+tails (3.0~beta4) unstable; urgency=medium
 
   * Major changes
     - All changes brought by Tails 2.12.
@@ -60,7 +60,7 @@ tails (3.0~beta4) UNRELEASED; urgency=medium
         for unmounted vfat and LUKS-encrypted ext4.
       · Run erase_memory a bit later, it requires less disk space nowadays.
 
- -- Tails developers <tails@boum.org>  Mon, 17 Apr 2017 17:37:04 +0000
+ -- Tails developers <tails@boum.org>  Tue, 18 Apr 2017 13:01:25 +0000
 
 tails (2.12) UNRELEASED; urgency=medium