Add missing override keywords

Change-Id: Id4fe5ffb27dbd3e96add0e87c1679b5b1ff76545
Reviewed-by: Gabriel de Dietrich <gabriel.dedietrich@qt.io>

src/plugins/platformthemes/flatpak/qflatpaktheme.h

@@ -72,7 +72,7 @@ public:
 
     QPixmap standardPixmap(StandardPixmap sp, const QSizeF &size) const override;
     QIcon fileIcon(const QFileInfo &fileInfo,
-                   QPlatformTheme::IconOptions iconOptions = 0) const;
+                   QPlatformTheme::IconOptions iconOptions = 0) const override;
 
     QIconEngine *createIconEngine(const QString &iconName) const override;