Fix mailing address in README.

Task-number: QTBUG-32390
Change-Id: Ia3a45897b0b7a6bb2434297b21c45bf2dbdda0a5
Reviewed-by: Laszlo Papp <lpapp@kde.org>
Reviewed-by: Shawn Rutledge <shawn.rutledge@digia.com>