[DOCS] Update 8.16.2.asciidoc (#118878)

Add note

Author: leemthompo

docs/reference/release-notes/8.16.2.asciidoc

@@ -1,6 +1,11 @@
 [[release-notes-8.16.2]]
 == {es} version 8.16.2
 
+[IMPORTANT]
+====
+The 8.16.2 release contains a fix for a potential security vulnerability. See our https://discuss.elastic.co/c/announcements/security-announcements/31[security advisory] for more details.
+====
+
 Also see <<breaking-changes-8.16,Breaking changes in 8.16>>.
 
 [[bug-8.16.2]]