UI: Always hide VScrollArea horizontal scroll bar

There appears to be a bug with displaying the vertical scroll bar widget
where the horizontal scroll bar will show when it's not supposed to.
Fortunately it can be completely disabled.

obs/vertical-scroll-area.hpp

@@ -11,6 +11,7 @@ public:
 	inline VScrollArea(QWidget *parent = nullptr)
 		: QScrollArea(parent)
 	{
+		setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
 	}
 
 protected: