Fix a few things in ExclusiveGroup documentation.
Fix a few things in ExclusiveGroup documentation.

Change-Id: I4feda741c7052e06f066c2ea69ba242a11b62b04
Reviewed-by: Gabriel de Dietrich <57b5c683f0b6abfc17ef151d5b68c8944258b63a@digia.com>

mizukusak/qtquickcontrols,drgvond/qtquickcontrols,mizukusak/qtquickcontrols,kobolabs/qtquickcontrols,kobolabs/qtquickcontrols,drgvond/qtquickcontrols,mizukusak/qtquickcontrols,drgvond/qtquickcontrols,kobolabs/qtquickcontrols