Fix pri file generation
Summary: The typo probably has been there for quite some time, but only a recent ECM change made it break (D26394)
Reviewers: KDE PIM, mlaurent, vkrause
Reviewed By: KDE PIM, vkrause
Subscribers: kde-pim
Tags: KDE PIM
Differential Revision: https://phabricator.kde.org/D27232