[krdb] Drop GTK2 colour exporting
Summary:
With the vast supermajority of modern GTK2 themes using pixmaps, exporting colours
is only likely to result in breakage.
BUG: 412331
FIXED-IN: 5.19.0 (or should we consider this a bugfix and land it on the stable branch?)
Reviewers: Plasma, ngraham, gikari, davidedmundson
Reviewed By: Plasma, ngraham, davidedmundson
Subscribers: gikari, fvogt, ngraham, plasma-devel
Tags: Plasma
Differential Revision: https://phabricator.kde.org/D28658