Qt: Retranslate GameList header and Filter line

Didn't notice this until I was trying to change the default font
to Comic Sans MS when language is set to English in yuzu.

src/citra_qt/game_list_p.h

@@ -431,6 +431,9 @@ public:
     void setFocus();
 
 private:
+    void changeEvent(QEvent*) override;
+    void RetranslateUI();
+
     class KeyReleaseEater : public QObject {
     public:
         explicit KeyReleaseEater(GameList* gamelist, QObject* parent = nullptr);