Make conflict dialog much bigger, it's unusable otherwise.

Summary:
The default size is tiny, which can make people miss some
important information, click on the wrong button, lose data, and
therefore shout at, for instance, their husband who maintains the
application in question ;)

Test Plan:
tested in the fork (precursor) of this code in FatCRM, not tested
here, but it's the same code.

Reviewers: krake, dvratil, mlaurent

Reviewed By: mlaurent

Subscribers: #kde_pim

Tags: #kde_pim

Differential Revision: https://phabricator.kde.org/D9251