Increase org_kde_plasma_shell interface version

Summary:
It was forgotten in 10b00a219e to increase org_kde_plasma_shell version
in the xml file, which leads to broken implementation.

Reviewers: Plasma, sharvey, bshah

Reviewed By: Plasma, bshah

Subscribers: bshah, kde-frameworks-devel

Tags: Frameworks

Differential Revision: https://phabricator.kde.org/D13076