Add usecases controller to documentation

Per a previous review comment, added a comment about the usecases
controller being reintroduced with the Guilin release.

Issue-ID: POLICY-2889
Change-Id: Ie52535e7e5cf653b74c35ba40b9af5ce28befe06
Signed-off-by: Jim Hahn <jrh3@att.com>
diff --git a/docs/release-notes.rst b/docs/release-notes.rst
index 3f0975a..181b725 100644
--- a/docs/release-notes.rst
+++ b/docs/release-notes.rst
@@ -64,6 +64,8 @@
    - Automated certificate generation
 * Actor Model
    - Support various use cases and provide more flexibility to Policy Designers
+   - Reintroduced the "usecases" controller into drools-pdp, supporting the use cases
+     under the revised actor architecture
 * Guard Application
    - Support policy filtering
 * Matchable Application