vty-ref: Update URI of docbook 5.0 schema

... to match the /etc/xml/catalog file on debian (no "www" in hostname)

Change-Id: Id9f3579c7f2bc3af13fe30b5268f249b6f59ed0d
1 file changed
tree: cb8ece4d543bb6878a36fc19025b642982cf0480
  1. doc/