Mention removal of VTL support in 2.16 release notes

Change-Id: I37089b680096e3852be7ae833e74d4d9e829b322
diff --git a/releases/2.16.md b/releases/2.16.md
index 12c2233..0a94e25 100644
--- a/releases/2.16.md
+++ b/releases/2.16.md
@@ -32,6 +32,15 @@
 indexes offline. These will automatically be reindexed by the online reindexer
 after starting Gerrit.
 
+### Support for Velocity templates removed
+
+In version 2.15 support for Soy templates was added. For backwards compatibility
+support for Velocity templates (VTL) was kept.
+
+In version 2.16 support for VTL is completely removed. Site administrators must
+replace any Velocity templates (*.vm) with the equivalent Soy templates before
+upgrading to this version.
+
 ## New Features
 
 ### REST API