Drop Qt 5 support

Qt 6 has been available for almost 4 years. Qt 5 is no longer officially supported by Qt for opensource, it's time to drop Qt 5.

src/device/devicemanager.cpp

@@ -107,11 +107,7 @@ DeviceManager::DeviceManager(Application *app, QObject *parent)
   QObject::connect(this, &DeviceManager::DeviceCreatedFromDB, this, &DeviceManager::AddDeviceFromDB);
 
   // This reads from the database and contents on the database mutex, which can be very slow on startup.
-#if QT_VERSION >= QT_VERSION_CHECK(6, 0, 0)
   (void)QtConcurrent::run(&thread_pool_, &DeviceManager::LoadAllDevices, this);
-#else
-  (void)QtConcurrent::run(&thread_pool_, this, &DeviceManager::LoadAllDevices);
-#endif
 
   // This proxy model only shows connected devices
   connected_devices_model_ = new DeviceStateFilterModel(this);

src/device/deviceproperties.cpp

@@ -243,11 +243,7 @@ void DeviceProperties::UpdateFormats() {
     // Get the device's supported formats list.  This takes a long time and it blocks, so do it in the background.
     supported_formats_.clear();
 
-#if QT_VERSION >= QT_VERSION_CHECK(6, 0, 0)
     QFuture<bool> future = QtConcurrent::run(&ConnectedDevice::GetSupportedFiletypes, device, &supported_formats_);
-#else
-    QFuture<bool> future = QtConcurrent::run(std::bind(&ConnectedDevice::GetSupportedFiletypes, device, &supported_formats_));
-#endif
     QFutureWatcher<bool> *watcher = new QFutureWatcher<bool>();
     QObject::connect(watcher, &QFutureWatcher<bool>::finished, this, &DeviceProperties::UpdateFormatsFinished);
     watcher->setFuture(future);

src/device/macosdevicelister.h

@@ -111,11 +111,8 @@ class MacOsDeviceLister : public DeviceLister {
   static QSet<MTPDevice> sMTPDeviceList;
 };
 
-#if QT_VERSION >= QT_VERSION_CHECK(6, 0, 0)
 size_t qHash(const MacOsDeviceLister::MTPDevice &device);
-#else
-uint qHash(const MacOsDeviceLister::MTPDevice &device);
-#endif
+
 inline bool operator==(const MacOsDeviceLister::MTPDevice &a, const MacOsDeviceLister::MTPDevice &b) {
   return (a.vendor_id == b.vendor_id) && (a.product_id == b.product_id);
 }

src/device/macosdevicelister.mm

@@ -101,11 +101,7 @@ class ScopedIOObject {
 
 QSet<MacOsDeviceLister::MTPDevice> MacOsDeviceLister::sMTPDeviceList;
 
-#if QT_VERSION >= QT_VERSION_CHECK(6, 0, 0)
 size_t qHash(const MacOsDeviceLister::MTPDevice &d) {
-#else
-uint qHash(const MacOsDeviceLister::MTPDevice &d) {
-#endif
   return qHash(d.vendor_id) ^ qHash(d.product_id);
 }