Documentation for QFontMetrics::height() is wrong

In the documentation for QFontMetrics::height() it refers to the +1 which was previously added to the height of fonts in Qt.

While the baseline is a one-dimensional metric, and does not have a vertical size, in Qt 4, we would add 1 to the height of fonts and then subtract 1 from the descent in all layout code to compensate.

In Qt 5 this was fixed, but the documentation was not updated.