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: db6df4cd70a25139991b443993b943bf6d1df008
  1. doc/