Fixed QxtSortFilterProxyModel docs.
Fixed QxtSortFilterProxyModel docs.

hrobeers/qxtweb-qt5,hrobeers/qxtweb-qt5,hrobeers/qxtweb-qt5,mmitkevich/libqxt,mmitkevich/libqxt,hrobeers/qxtweb-qt5,mmitkevich/libqxt,mmitkevich/libqxt,hrobeers/qxtweb-qt5