Adapt to changes in KBookmarks >= 5.69

Test Plan:
The Bookmarks menu is still added as expected and the actions still show
in the configure shortcuts dialog. I couldn't test actually creating a
bookmark as I have no access to remote servers.

Reviewers: cfeck, uwolfer, murrant

Reviewed By: cfeck

Differential Revision: https://phabricator.kde.org/D28920