Remove utils.h

Summary:
With this we no longer have QtXmlPatterns, QtXml or KIO in the public
interface (which is what the CMake config file has been claiming all
along).

Reviewers: mlaurent

Reviewed By: mlaurent

Subscribers: kde-pim

Tags: #kde_pim

Differential Revision: https://phabricator.kde.org/D24295