[Rdo-list] [tripleo] Outdated link to instack-undercloud documentation

[Alan Pevec]

> I did the same mistake some months ago, I suggest to clean this
> repository up. I pushed a PR for that
> https://github.com/rdo-management/instack-undercloud/pull/7


What about other ex "midstream" repos in
https://github.com/rdo-management/ ?

Maybe best to remove them all?

Cheers,
Alan