Geo: Stale docs on frequency of Geo replication

@skarbek referred to this section in the docs: https://docs.gitlab.com/ee/administration/geo/replication/faq.html#how-long-does-it-take-to-have-a-commit-replicated-to-a-secondary-node

All replication operations are asynchronous and are queued to be dispatched in a batched request every 10 minutes. Besides that, it depends on a lot of other factors including the amount of traffic, how big your commit is, the connectivity between your nodes, your hardware, etc.

This is incorrect now and needs updating.