Add OVN-K update to CI/CD maintenance docs

[dfarrell07]

We should document that the version of OVN-K in Shipyard needs to be manually updated each release.

https://github.com/submariner-io/shipyard/blob/devel/scripts/shared/lib/clusters_kind#L277

We have docs for this kind of thing here:

https://submariner.io/development/building-testing/ci-maintenance/

[dfarrell07]

Related: submariner-io/shipyard#1830

So it looks like it's the image hash that needs to be updated.

[dfarrell07]

Related: submariner-io/submariner#3284

Also the go.mod and any code changes in other repos.