Change wording in QML Tutorial.

Task-number: QTBUG-25595

Change-Id: I38b227ac2652d2b04d3d1e00f397d189a9de4bed
Reviewed-by: Venugopal Shivashankar <venugopal.shivashankar@digia.com>
Reviewed-by: Alan Alpert <aalpert@blackberry.com>
Reviewed-by: Jerome Pasion <jerome.pasion@digia.com>