Fix the low pixel size limit in Scale to New Size dialog

Summary:
This commit changes the limit for image size
in the dialog from 90k pixels to 100000k (100M) pixels
which is the same limit as in the File -> New dialog.

BUG:395267

Test Plan:

• trying to scale image to 1000M pixels in any dimension

(dialog should not allow for that)

• trying to scale image to 1000M pixels, but in a different

unit (according to dpi); dialog should not allow for that

• trying to scale image to 20k pixels, it works fine

Reviewers: Krita, woltherav

Reviewed By: Krita, woltherav

Subscribers: woltherav

Tags: Krita

Differential Revision: https://phabricator.kde.org/D19545