Mark Tails 3.10 as released.

debian/changelog

-tails (3.10) UNRELEASED; urgency=medium
+tails (3.10) unstable; urgency=medium
 
   * Security fixes
     - Harden sudo config to avoid potential future privilege escalation
@@ -46,7 +46,7 @@ tails (3.10) UNRELEASED; urgency=medium
     - Update test suite for updated button labels in confirmation dialogs
       of the Tails installer (Closes: #11501).
 
- -- Tails developers <tails@boum.org>  Mon, 22 Oct 2018 15:50:55 +0200
+ -- Tails developers <tails@boum.org>  Tue, 23 Oct 2018 01:30:00 +0200
 
 tails (3.9.1) unstable; urgency=medium