[DOCS] Fix shrink index API prereqs

[joegallo]

It's not actually the case that all the primaries need to be on the same node, replicas are sufficient. I think this got switched to the incorrect wording in #59985 -- so the docs should be fixed back to 7.8 branch if we're doing a completion run.

[elasticmachine]

Pinging @elastic/es-docs (Team:Docs)

[elasticmachine]

Pinging @elastic/es-data-management (Team:Data Management)

[jrodewig]

Thanks for fixing this @joegallo. Let me know if you need any help backporting this fix.

[joegallo]

@jrodewig I backported as far as 7.17 -- do you have tooling to make this easier for the older branches, or are you manually cherry-picking and pushing? Also what's the etiquette on PR labels for those older branches/backports?

If it's as simple as "yeah, indeed, add a label for all those versions, then cherry-pick and push" then I can just do that.

[jrodewig]

do you have tooling to make this easier for the older branches, or are you manually cherry-picking and pushing?

I use the backport tool and temporarily edit .backportrc.json to add the missing branches. Cherry-picking and pushing should work fine too.

what's the etiquette on PR labels for those older branches/backports?

We add a label for those versions.

[joegallo]

👍, all good, I can handle that then. Thanks!