[kcm-colors] Do not ship any additional color schemes

Summary: This patch removes the extra color schemes we have been shipping for quite a while. Reasoning is explained in Phabricator task T10497.

Test Plan:
delete the contents of `usr/share/color-schemes/`

{F6880378}

Reviewers: #plasma, #vdg, ngraham

Reviewed By: #vdg, ngraham

Subscribers: broulik, abetts, davidedmundson, nicolasfella, plasma-devel

Tags: #plasma

Maniphest Tasks: T10497

Differential Revision: https://phabricator.kde.org/D21701