Fix progress size while printing
Summary:
Use QSpacerItem::changeSize() to fix the size when printing or not.
This Forces our Progress bar to use as much of the space as it can
Reviewers: tcanabrava, patrickelectric, laysrodrigues
Reviewed By: laysrodrigues
Subscribers: Atelier: AtCore
Tags: Atelier: AtCore
Differential Revision: https://phabricator.kde.org/D12267