Update validator-failover.md

[schmiatz]

i kicked out the old etcd method, as thats not recommended to use. etcd is not very reliable and this introduces a single point of failure that is not necessary.
Ive basically used pumpkins guide from here https://pumpkins-pool.gitbook.io/pumpkins-pool and updated the readme accordingly.

[bartenbach]

I might be biased, but I think this change should be made.

Nobody uses etcd and it's not recommended by anybody. We usually have to end up linking my gitbook document. Makes more sense to have this in the docs.

[steviez]

I saw that this was attempted previously in #3683. However, that PR never moved out of Draft state so it wasn't clear if it was ever ready.

As for the actual intent, it seems like most validator operators are using the newer approach over etcd. I can possibly take a look here, but I might see if @tigarcia is comfortable reviewing or if we can find someone else if not

[tigarcia]

Overall a great change. I have some wording requests.

[steviez]

The content in general looks look, just a couple formatting / grammatical nitpicks and then I'll think this will be good to go

[steviez]

LGTM, thanks!

[steviez]

CI says you have a bunch of trailing whitespace; please remove that (typically as simple as a setting in your editor):
https://buildkite.com/anza/agave/builds/20219#01957994-44b8-4e8c-8e3c-bb938e7f7068