Remove note about reusing the render widget.

This is actually not possible due to how Qt manages child widgets...

Source/Core/DolphinQt/MainWindow.h

@@ -65,7 +65,7 @@ private:
 	QString ShowFileDialog();
 	void DoStartPause();
 
-	std::unique_ptr<DRenderWidget> m_render_widget; // TODO: just create this once and reuse it
+	std::unique_ptr<DRenderWidget> m_render_widget;
 	bool m_isStopping = false;
 };