fixed table headers for db parameter in online backup docs (#909)

Cherry-picked from #901

Co-authored-by: Christophe Willemsen <[email protected]>

Author: renetapopova

modules/ROOT/pages/backup-restore/online-backup.adoc

@@ -80,8 +80,8 @@ neo4j-admin database backup [-h] [--expand-commands] [--verbose]
 [options="header", cols="1m,3a,1m"]
 |===
 | Parameter
-| Default
 | Description
+| Default
 
 |<database>
 |Name of the remote database to backup. Can contain `*` and `?` for globbing (required unless `--inspect-path` is used).