[Website]: ES|QL query across clusters tutorial needs remote cluster setup instructions to be pulled out

[shainaraskas]

Type of issue

Other

What documentation page is affected

https://www.elastic.co/docs/reference/query-languages/esql/esql-cross-clusters

What happened?

This info is aging / not necessarily relevant for all deployment types. Instead of explaining remote cluster setup in this doc, we should reference the core remote cluster docs

Additional info

No response