refactor: Remove manual high-dpi support

This removes the --scale command line option.
Qt6 seems to have this already integrated to scale according to the
nativ display settings: https://doc.qt.io/qt-6.8/highdpi.html
Adjusting the scale on a per-application basis is not intended (anymore)
according to the documentation.
Tested on a (near) high-dpi screen.

src/swiftlauncher/main.cpp

@@ -35,7 +35,6 @@ void initDbCacheFromResourceFileIfRequired(CGuiApplication &a)
 
 int main(int argc, char *argv[])
 {
-    CGuiApplication::highDpiScreenSupport(CGuiApplication::scaleFactor(argc, argv));
     QApplication qa(argc, argv); // needed
     Q_UNUSED(qa)
     CGuiApplication a(CApplicationInfo::swiftLauncher(), CApplicationInfo::Launcher, CIcons::swiftLauncher1024());