DolphinQt: Fix ElidedButton (MappingButton) from growing with long text.

Source/Core/DolphinQt/QtUtils/ElidedButton.h

@@ -12,10 +12,13 @@ class ElidedButton : public QPushButton
 public:
   explicit ElidedButton(const QString& text = QStringLiteral(""),
                         Qt::TextElideMode elide_mode = Qt::ElideRight);
+
   Qt::TextElideMode elideMode() const;
   void setElideMode(Qt::TextElideMode elide_mode);
 
+  QSize sizeHint() const final override;
+
 private:
-  void paintEvent(QPaintEvent* event) override;
+  void paintEvent(QPaintEvent* event) final override;
   Qt::TextElideMode m_elide_mode;
 };