BlackBerry: remove unused settings key

Change-Id: I09a69029d659f5a9caf9a062233fad8b3737583a
Reviewed-by: David Kaspar <dkaspar@blackberry.com>
Reviewed-by: Nicolas Arnaud-Cormos <nicolas@kdab.com>
Reviewed-by: Mehdi Fekari <mfekari@blackberry.com>