Mark Beijing as security not supported

According to our Vulnerability Management Procedure currently we
support only master branch and the latest release.

Let's make our users fully aware of that by adding a suitable note to
our security release notes.

Issue-ID: SECCOM-216
Change-Id: I444d8e813745d7c0ece8e4417ee7ac45a2ea6549
Signed-off-by: Krzysztof Opasiak <k.opasiak@samsung.com>
diff --git a/docs/release/index.rst b/docs/release/index.rst
index 3139479..ccdef0b 100644
--- a/docs/release/index.rst
+++ b/docs/release/index.rst
@@ -155,6 +155,10 @@
 Project specific details are in the :ref:`release notes<doc-releaserepos>`
 for each project.
 
+**Please note that this version is no longer supported in terms of security bug fixes.
+It means that community is not going to backport any security improvements introduced in master nor fix any reported vulnerabilities.
+Please upgrade to newer release.**
+
 Licenses
 ========
 ONAP Source Code is licensed under the `Apache Version 2 License