Include the removal of Assignee feature in the v3.6 release notes

Change-Id: Ib0e7007f98c361e61c169d5c6b0a3997ef1a7a7f
diff --git a/pages/site/releases/3.6.md b/pages/site/releases/3.6.md
index b717492..66cff88 100644
--- a/pages/site/releases/3.6.md
+++ b/pages/site/releases/3.6.md
@@ -115,6 +115,13 @@
 
 ### Breaking changes
 
+* [Change 321607](https://gerrit-review.googlesource.com/321607):
+  _Assignee_ feature is completely removed from the Gerrit UI
+
+  The Attention Set feature has been launched in Gerrit v3.3, and assignee
+  has been turned off by default for three releases. The feature is now completely
+  removed and cannot be enabled anymore by config.
+
 * [Project Owners implicit delete reference permission has been removed](https://gerrit-review.googlesource.com/c/gerrit/+/304054).
 
   Before this release all Project Owners had implicit delete permission to all