Qt: Remove unused variables

* The usage for this one was removed in
  be3e884ba5
* This one is not used since afae3c8b80
  which moved the whole refresh process into its own method
* I couldn't find any usage of this one in the history, it was probably
  never read.
* This one was used until 10d5588d4c which
  removed the usage but not the declaration
* Unused since cf7017dd86

src/platform/qt/GBAApp.cpp

@@ -112,7 +112,6 @@ Window* GBAApp::newWindow() {
 		return nullptr;
 	}
 	Window* w = new Window(&m_manager, m_configController, m_multiplayer.attached());
-	int windowId = m_multiplayer.attached();
 	connect(w, &Window::destroyed, [this, w]() {
 		m_windows.removeAll(w);
 		for (Window* w : m_windows) {

src/platform/qt/GBAKeyEditor.cpp

@@ -36,7 +36,6 @@ GBAKeyEditor::GBAKeyEditor(InputController* controller, int type, const QString&
 	setWindowFlags(windowFlags() & ~Qt::WindowFullscreenButtonHint);
 	setMinimumSize(300, 300);
 
-	const mInputMap* map = controller->map();
 	controller->stealFocus(this);
 
 	m_keyDU = new KeyEditor(this);

src/platform/qt/InputController.cpp

@@ -771,7 +771,6 @@ void InputController::prepareCamSettings(QCamera::Status status) {
 		return;
 	}
 #if (QT_VERSION >= QT_VERSION_CHECK(5, 5, 0))
-	QVideoFrame::PixelFormat format(QVideoFrame::Format_RGB32);
 	QCameraViewfinderSettings settings;
 	QSize size(1280, 720);
 	auto cameraRes = m_camera->supportedViewfinderResolutions(settings);
@@ -791,7 +790,6 @@ void InputController::prepareCamSettings(QCamera::Status status) {
 	for (const auto& goodFormat : goodFormats) {
 		if (cameraFormats.contains(goodFormat)) {
 			settings.setPixelFormat(goodFormat);
-			format = goodFormat;
 			goodFormatFound = true;
 			break;
 		}

src/platform/qt/MemoryModel.cpp

@@ -336,7 +336,6 @@ void MemoryModel::paintEvent(QPaintEvent* event) {
 	static QChar c0('0');
 	static QString arg("%0");
 	static QString arg2("%0:%1");
-	QSizeF letterSize = QSizeF(m_letterWidth, m_cellHeight);
 	painter.drawStaticText(QPointF((m_margins.left() - m_regionName.size().width() - 1) / 2.0, 0), m_regionName);
 	painter.drawText(
 	    QRect(QPoint(viewport()->size().width() - m_margins.right(), 0), QSize(m_margins.right(), m_margins.top())),

src/platform/qt/MemorySearch.cpp

@@ -40,7 +40,6 @@ bool MemorySearch::createParams(mCoreMemorySearchParams* params) {
 	if (m_ui.searchROM->isChecked()) {
 		params->memoryFlags |= mCORE_MEMORY_READ;
 	}
-	mCore* core = m_controller->thread()->core;
 
 	QByteArray string;
 	bool ok = false;