Qt: Change settings dialogs to widgets/windows

Stops them breaking in Qt 6.6.

src/duckstation-qt/displaysettingswidget.h

@@ -8,14 +8,14 @@
 #include "ui_displaysettingswidget.h"
 
 class PostProcessingChainConfigWidget;
-class SettingsDialog;
+class SettingsWindow;
 
 class DisplaySettingsWidget : public QWidget
 {
   Q_OBJECT
 
 public:
-  DisplaySettingsWidget(SettingsDialog* dialog, QWidget* parent);
+  DisplaySettingsWidget(SettingsWindow* dialog, QWidget* parent);
   ~DisplaySettingsWidget();
 
 private Q_SLOTS:
@@ -29,5 +29,5 @@ private:
 
   Ui::DisplaySettingsWidget m_ui;
 
-  SettingsDialog* m_dialog;
+  SettingsWindow* m_dialog;
 };