Release note for resource update restrict

Adds release note for update/replace restriction
feature.

Change-Id: I9063013dd34e54621e387d60cb2de376b2848872
Blueprint: stack-update-restrict

releasenotes/notes/restrict_update_replace-68abece58cf3f6a0.yaml

@@ -0,0 +1,7 @@
+---
+features:
+  - Adds a new feature to restrict update or replace of
+    a resource when a stack is being updated. Template
+    authors can set ``restricted_actions`` in the ``resources``
+    section of ``resource_registry`` in an environment file
+    to restrict update or replace.