Fix minor documentation typos
Summary:
These typos show up in the generated manpages.
Reviewers: Frameworks, alexmerry, kossebau, cgiboudeaux
Reviewed By: cgiboudeaux
Subscribers: cgiboudeaux, kde-frameworks-devel, kde-buildsystem
Tags: Frameworks, Build System
Differential Revision: https://phabricator.kde.org/D12867