kamilio.cfg: updated the address of sr-users mailing list

etc/kamailio.cfg

@@ -4,7 +4,7 @@
 #     - web: http://www.kamailio.org
 #     - git: http://sip-router.org
 #
-# Direct your questions about this file to: <sr-users@lists.sip-router.org>
+# Direct your questions about this file to: <sr-users@lists.kamailio.org>
 #
 # Refer to the Core CookBook at http://www.kamailio.org/wiki/
 # for an explanation of possible statements, functions and parameters.