Fix some qt6 compile error

libdiscover/DiscoverBackendsFactory.h

@@ -9,9 +9,8 @@
 
 #include "discovercommon_export.h"
 #include <QList>
-
+#include <QStringList>
 class QCommandLineParser;
-class QStringList;
 class AbstractResourcesBackend;
 
 class DISCOVERCOMMON_EXPORT DiscoverBackendsFactory

libdiscover/utils.h

@@ -122,13 +122,13 @@ static QVector<T> kSetToVector(const QSet<T> &set)
         ret.append(x);
     return ret;
 }
-
+#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
 template<typename T>
 static QSet<T> kToSet(const QVector<T> &set)
 {
     return QSet<T>(set.begin(), set.end());
 }
-
+#endif
 template<typename T>
 static QSet<T> kToSet(const QList<T> &set)
 {

notifier/main.cpp

@@ -26,8 +26,9 @@ int main(int argc, char **argv)
 {
     QApplication app(argc, argv);
     app.setOrganizationDomain(QStringLiteral("kde.org"));
+#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
     app.setAttribute(Qt::AA_UseHighDpiPixmaps, true);
-
+#endif
     KCrash::setFlags(KCrash::AutoRestart);
 
     NotifierItem notifier;