Deprecate KDBusConnectionPool
Summary:
As per T12722 this is no longer needed, QDBusConnection now behaves
correctly in a multi-threaded scenario.
All uses found by lxr have either been ported already, or have patches
in review.
Reviewers: davidedmundson
Reviewed By: davidedmundson
Subscribers: kossebau, kde-frameworks-devel
Tags: Frameworks
Differential Revision: https://phabricator.kde.org/D27607