Make Breeze Dark use same Kolourpaint icon as Breeze

Summary:
For a while now, Breeze Dark icons have had a different Kolourpaint icon. I think the Breeze version looks better and has better contrast, plus it's good to use consistent icons.

Also, reduce size and format code

Test Plan:
Old:

New:

Reviewers: VDG, filipf, ngraham

Reviewed By: VDG, filipf, ngraham

Subscribers: kde-frameworks-devel

Tags: Frameworks

Differential Revision: https://phabricator.kde.org/D21521