QmlDesigner.propertyEditor: reduce delay

Since we changed the slection behaivour after drag and drop
this makes the designer more responsive.

Change-Id: I21c14a126ff0b63151002ac51e841a624b43e879
Reviewed-on: http://codereview.qt.nokia.com/2033


Reviewed-by: Thomas Hartmann <Thomas.Hartmann@nokia.com>