UI: retranslate the game list placeholder

This is the "Double-click to add a new folder to the game list" message
that shows up when users first launch yuzu and is most likely never seen
again. Previously this message was not re-translated.

src/yuzu/game_list.h

@@ -166,6 +166,9 @@ protected:
     void mouseDoubleClickEvent(QMouseEvent* event) override;
 
 private:
+    void changeEvent(QEvent* event) override;
+    void RetranslateUI();
+
     QVBoxLayout* layout = nullptr;
     QLabel* image = nullptr;
     QLabel* text = nullptr;