centos: Remove URLs pointing to vault.centos.org

As vault.centos.org doesn't keep any ISO anymore, let's just remove them
from our db.

Along with the URLs removal, let's remove together the tree's as those
can't be accessed without a valid URL.

Removing all the vault.centos.org URLs matches with the recommendation
given by CentOS folks in #centos-devel:
"so in short, if some program links to vault, it's most likely not a
good idea and may not even work"

Signed-off-by: Fabiano Fidêncio <fidencio@redhat.com>
Reviewed-by: Christophe Fergeau <cfergeau@redhat.com>