qdoc: Added excludedirs to qtquickdialogs.qdocconf

Added excludedirs += ../qml to qtquickdialogs.qdocconf.

Task-number: QTBUG-33966
Change-Id: I08a74061ed82301712239bc0979ed6fcea0a2448
Reviewed-by: Shawn Rutledge <shawn.rutledge@digia.com>
Reviewed-by: Jerome Pasion <jerome.pasion@digia.com>