doc: Remove references to dead VMWare NSX extensions
doc: Remove references to dead VMWare NSX extensions

There are a number of extensions that were removed from the vmware-nsx
package as part of the removal of NSX-MH support in 15.0.0 (October
2019) [1]. We don't need to keep references to these. You can prove this
by grepping for the various references config options in the current
source tree and using 'git log -S' to find the patches that removed
things.

[1] https://opendev.org/x/vmware-nsx/commit/26135f34acca66ce994e0dd4280e2e968ed10ce3

Change-Id: I6f4489b14b164e4699a600acac84065dfe1231dc
Signed-off-by: Stephen Finucane <492121341a95b3c3aab646bed44634f739dd019b@redhat.com>

openstack/neutron,openstack/neutron,mahak/neutron,mahak/neutron,openstack/neutron,mahak/neutron