Restrict Qt::AA_UseHighDpiPixmaps to Qt5.

src/main.cpp

@@ -92,7 +92,9 @@ int Q_DECL_IMPORT main(int argc, char* argv[])
     aboutData.setHomepage(QStringLiteral("https://www.kde.org/applications/system/partitionmanager"));
 
     KAboutData::setApplicationData(aboutData);
+#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
     app.setAttribute(Qt::AA_UseHighDpiPixmaps, true);
+#endif
     KCrash::initialize();
 
     QCommandLineParser parser;