D19938: Avoid deprecated QRegion::subtract()

[Dag Andersen]

danders accepted this revision.
This revision is now accepted and ready to land.

REPOSITORY
  R8 Calligra

REVISION DETAIL
  https://phabricator.kde.org/D19938

To: pvuorela, #calligra:_3.0, danders
Cc: Calligra-Devel-list, dcaliste, cochise, vandenoever