[potd dataengine] Remove unused X-KDE-PlasmaPoTDProvider-SuffixType
Summary:
Not used by code at least since this dataengine was moved to
kdeplasma-addons in 2009 in 627cf5683a55699a78f09bc4b0f670d11e3908cf
Test Plan: All providers still work
Reviewers: xuetianweng, davidedmundson
Reviewed By: davidedmundson
Subscribers: plasma-devel
Tags: Plasma
Differential Revision: https://phabricator.kde.org/D11952