Add link to security documentation for Elasticsearch 6.5

Change-Id: I52eb2953d0f588ce25f9c229f4d8d1be50296166
diff --git a/Documentation/config-gerrit.txt b/Documentation/config-gerrit.txt
index dcc875c..88e1d11 100644
--- a/Documentation/config-gerrit.txt
+++ b/Documentation/config-gerrit.txt
@@ -2944,6 +2944,7 @@
 * link:https://www.elastic.co/guide/en/x-pack/6.2/security-getting-started.html[Elasticsearch 6.2]
 * link:https://www.elastic.co/guide/en/elastic-stack-overview/6.3/security-getting-started.html[Elasticsearch 6.3]
 * link:https://www.elastic.co/guide/en/elastic-stack-overview/6.4/security-getting-started.html[Elasticsearch 6.4]
+* link:https://www.elastic.co/guide/en/elastic-stack-overview/6.5/security-getting-started.html[Elasticsearch 6.5]
 
 [[elasticsearch.username]]elasticsearch.username::
 +