remove "cross-continent" line from cross-config docs

[jess-edwards]

@jseldess

Can you remove the line "cross-continent scenarios will be better supported in the future" from the config page?

Per @dianasaur323 - this language is too vague and should cleared up when the expressive zine config docs are live.

[dianasaur323]

@jseldess Ok - synced up with Ben. Apparently we are no longer recommending the raft tick interval config, so we should remove that. He also suggested using the term inter-contient versus cross-continent. On the cross-continent scenarios will be better supported in the future, let's do "cross-continent scenarios will improve in performance soon", and we can link over to the reactive lease RFC when Alex finishes writing it.

[jseldess]

Got it, thanks, @dianasaur323. As part of #1027, I've already removed the raft tick interval part. In that PR, I'll also revise the language as suggested.