Mark Tails 4.9 as released.

debian/changelog

-tails (4.9) UNRELEASED; urgency=medium
+tails (4.9) unstable; urgency=medium
 
   * Security fixes
     - Upgrade Tor Browser to 9.5.3-build1 (Closes: #17827).
@@ -46,7 +46,7 @@ tails (4.9) UNRELEASED; urgency=medium
     - Make the "the Tor Browser has started" step stricter.
     - Improve error output when the Unsafe Browser fails to start in some locale.
 
- -- Tails developers <tails@boum.org>  Mon, 27 Jul 2020 06:25:00 +0200
+ -- Tails developers <tails@boum.org>  Mon, 27 Jul 2020 09:03:10 +0200
 
 tails (4.8) unstable; urgency=medium