Documentation: Fix security mailing list address.

We don't own ovs.org, and I doubt Ojai Valley School would enjoy
receiving our email.

Reviewed-by: Greg Rose <gvrose8192@gmail.com>
Signed-off-by: Ben Pfaff <blp@ovn.org>

Documentation/internals/mailing-lists.rst

@@ -93,4 +93,4 @@ security
 The `security`__ mailing list is for submitting security vulnerabilities to the
 security team.
 
-__ security@ovs.org
+__ security@openvswitch.org