QML ColorDialog default/minimum size covers most of the screen

The intention was to do this only on small-screen devices, but on desktop machines it looks ridiculous. Even worse, the user cannot resize it smaller because of the minimum size. And because the systemdialogs example uses a QGuiApplication, the QML color dialog is the default on both KDE and Windows (because they would otherwise use a widget-based QColorDialog, but widgets are not available).