Summary:
KAboutData::setProgramIconName isn't used in the AboutData dialog box,
instead the generic QApplication icon name is used.

Therefore there's little point setting it. It was also used by classic
mode to create an icon in the config page that it has, but we can do
that directly.

Test Plan:
Compiles
Looked at module about data
Looked at settings page

Reviewers: #plasma, apol

Reviewed By: apol

Subscribers: plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D18489