Remove font-based QScrollArea sizeHint limit

QScrollArea::sizeHint uses QSize::boundedTo to limit the maximum size hint that it will return.

The upper bounds for the sizeHint are determined by the line height of the font associated with the widget, however this value has no real meaning for non-textual widgets. E.g., a QScrollArea showing an image should return a sizeHint based on the image size, not on a font which the widget is not using.

A better upper bound might be something like the screen size.