Remove kvmfornfv from Docs

Remove kvmfornfv from Docs

kvmfornfv isn't participating the Gambia release, and their project
contains further submodules which increases the time and space needed
for the docs builds.

When the project participates in the next release they can merge
https://gerrit.opnfv.org/gerrit/#/c/62481/ and use interphinx to link to
their docs.

Change-Id: Ifb353d1880b03fab37704ee97c073cf94676d954
Signed-off-by: Trevor Bramwell <tbramwell@linuxfoundation.org>