The given size is mostly ignored and the resulting pixmaps typically end up
in a QIcon, which will clobber the DPR anyways when returning a pixmap
for a given size.
Moreover, returning a message box icon with a DPR > 1 when
high DPI scaling is active and Qt::AA_UseHighDpiPixmaps is not set
causes the pixmap to become too small due to some scaling error.

Task-number: QTBUG-52622
Change-Id: I8aaaa97667d6c168040e19b7edad9dfb7517f70f
Reviewed-by: Morten Johan Sørvig <morten.sorvig@theqtcompany.com>