Fix GUI scaling issue on Linux

It seems `QT_AUTO_SCREEN_SCALE_FACTOR` doesn't work as expected.
Closes #6935.

src/app/main.cpp

@@ -102,10 +102,6 @@ void displayBadArgMessage(const QString &message);
 
 #if !defined(DISABLE_GUI)
 void showSplashScreen();
-
-#if defined(Q_OS_UNIX)
-void setupDpi();
-#endif  // Q_OS_UNIX
 #endif  // DISABLE_GUI
 
 // Main
@@ -120,10 +116,6 @@ int main(int argc, char *argv[])
     macMigratePlists();
 #endif
 
-#if !defined(DISABLE_GUI) && defined(Q_OS_UNIX)
-    setupDpi();
-#endif
-
     try {
         // Create Application
         QString appId = QLatin1String("qBittorrent-") + Utils::Misc::getUserIDString();
@@ -330,14 +322,6 @@ void showSplashScreen()
     QTimer::singleShot(1500, splash, &QObject::deleteLater);
     qApp->processEvents();
 }
-
-#if defined(Q_OS_UNIX)
-void setupDpi()
-{
-    if (qEnvironmentVariableIsEmpty("QT_AUTO_SCREEN_SCALE_FACTOR"))
-        qputenv("QT_AUTO_SCREEN_SCALE_FACTOR", "1");
-}
-#endif  // Q_OS_UNIX
 #endif  // DISABLE_GUI
 
 void displayVersion()