Add schema change information to 3.3 release notes

Change-Id: Ia03ce7505c7e4aaa9a7c52654fb7cb6c0512e13d
diff --git a/pages/site/releases/3.3.md b/pages/site/releases/3.3.md
index 36f89b4..a345997 100644
--- a/pages/site/releases/3.3.md
+++ b/pages/site/releases/3.3.md
@@ -18,6 +18,15 @@
 
 ### Schema Changes
 
+This release contains schema changes. To upgrade:
+
+``` sh
+  java -jar gerrit.war init -d site_path
+```
+
+Upgrading to this schema version (184) renames the `Non-Interactive Users`
+group to `Service Users`.
+
 ### Native Packaging
 
 ### Breaking Changes