Do not scroll pop-up palette when setting document offset

Summary:
QWidget::scroll(int dx, int dy) will scroll the widget including its
children. Since KisPopupPalette is a child of KisQPainterCanvas when
using the QPainter-based canvas we want to scroll only the widget
and not its children by calling QWidget::scroll(int dx, int dy,
const QRect &r) instead.

BUG:395375

Test Plan:

1. Click Settings > Configure Krita > Display
2. Uncheck "Canvas Graphics Acceleration" and click OK
3. File > New to create new document
4. Click "Freehand Brush Tool"
5. Right-click on canvas, rotate using wheel. The popup should not move.
6. Right-click on canvas, reset rotation by clicking at top circle of wheel. The popup should not move.
7. Right-click on canvas, zoom using zoom slider. The popup should not move.
8. Right-click on canvas, reset zoom to 100% by clicking "100%" button. The popup should not move,.

Reviewers: Krita, dkazakov

Reviewed By: Krita, dkazakov

Subscribers: dkazakov, Krita

Tags: Krita

Differential Revision: https://phabricator.kde.org/D13703