[www] Remove liberty Install Guide links
[www] Remove liberty Install Guide links

Remove the links to Install Guide, those are not published anymore.

Change-Id: I632bfe3f8315130e1adce01acd1a6a0547e9de3b

openstack/openstack-manuals,openstack/openstack-manuals,openstack/openstack-manuals,openstack/openstack-manuals