Document Unhealthy Geo status when Maintenance Mode is on

doc/administration/geo/disaster_recovery/planned_failover.md

...disaster_recovery/runbooks/planned_failover_multi_node.md

...isaster_recovery/runbooks/planned_failover_single_node.md

doc/administration/geo/replication/troubleshooting.md

...dministration/geo/replication/version_specific_updates.md