Update about data

Summary:
Currently, --about doesn't have any effect. In addition to that, the about
data contains outdated information.

This change hopefully addresses all previously mentioned issues.

Test Plan: Ran kwin_wayland --author.

Reviewers: KWin, graesslin

Reviewed By: KWin, graesslin

Subscribers: graesslin, kwin

Tags: KWin

Differential Revision: https://phabricator.kde.org/D17319