Replace "once" with "when" or "after"

doc/administration/auth/ldap/ldap-troubleshooting.md

doc/administration/geo/disaster_recovery/planned_failover.md

doc/administration/geo/index.md

doc/administration/geo/replication/configuration.md

doc/administration/geo/replication/remove_geo_site.md

doc/administration/geo/setup/database.md

doc/administration/geo/setup/external_database.md

doc/administration/git_protocol.md

doc/administration/gitaly/praefect.md

doc/administration/logs/tracing_correlation_id.md

doc/administration/maintenance_mode/index.md

...ration/monitoring/gitlab_self_monitoring_project/index.md

doc/administration/nfs.md