Revert "Reset QWidget's winId when backing window surface is destroyed"
This reverts commit a9246c7132a2c8864d3ae6cebd260bb9ee711fcb.
The QWidget machinery is way to fragile to reset the winId under the
feet of QWidget like that. We would potentially need to include all
the logic in QWidget::destroy. This also ties into the flow between
QtGui and QtWidgets during window closing, which is still unresolved.
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>
Reviewed-by: Volker Hilsheimer <firstname.lastname@example.org>