Fix the "Default" color scheme to match Breeze again

Summary:
Over the years, the "Default" color scheem seems to have drifted out of alignment with Breeze. Part of this was my doing, in https://cgit.kde.org/breeze.git/commit/?id=04dac01c2a3268f7f6189b2d5c404cb2b7aaf51f, but there were other changes too that were not reflected in the Default color scheme.

This patch fixes it to match Breeze again. There may be more patches required in other repos, which will be forthcoming as I discover more definitions of the default color scheme (this is the only once I've found so far).

Test Plan:

Reviewers: Breeze, Plasma, hein

Reviewed By: Plasma, hein

Subscribers: kde-frameworks-devel, cfeck, abetts

Tags: Frameworks

Differential Revision: https://phabricator.kde.org/D12392