Mark Tails 3.7.1 as released.

debian/changelog

-tails (3.7.1) UNRELEASED; urgency=medium
+tails (3.7.1) unstable; urgency=medium
 
   * Security fixes
     - Upgrade Tor Browser to 7.5.5 (MFSA 2018-14; closes: #15643).
@@ -36,7 +36,7 @@ tails (3.7.1) UNRELEASED; urgency=medium
   * Test suite
     - Update to match "Tails documentation" behaviour change.
 
- -- Tails developers <tails@boum.org>  Sat, 09 Jun 2018 15:22:28 +0000
+ -- Tails developers <tails@boum.org>  Sat, 09 Jun 2018 19:53:51 +0000
 
 tails (3.7) unstable; urgency=medium