Update changelog for 2.2.1.

debian/changelog

-tails (2.3) UNRELEASED; urgency=medium
+tails (2.2.1) unstable; urgency=medium
 
-  * Dummy entry.
+  * Security fixes
+    - Upgrade Tor Browser to 5.5.4. (Closes: #11254)
+    - Upgrade bind9-related packages to 1:9.9.5.dfsg-9+deb8u6
+    - Upgrade libotr to 4.1.0-2+deb8u1
+    - Upgrade samba-related packages to 2:4.1.17+dfsg-2+deb8u2.
+    - Upgrade libgraphite2 to 1.3.6-1~deb8u1.
 
- -- anonym <anonym@riseup.net>  Tue, 08 Mar 2016 20:42:39 +0100
+ -- Tails developers <tails@boum.org>  Thu, 17 Mar 2016 15:03:52 +0100
 
 tails (2.2) unstable; urgency=medium