[KCharSelect] Adapt the code to KBookmarks-5.69 changes

Test Plan:
The Bookmarks menu has the usual entries, and the bookmark actions are
displayed in the configure shortcuts dialog.

Reviewers: cfeck

Reviewed By: cfeck

Subscribers: asturmlechner, kde-utils-devel

Differential Revision: https://phabricator.kde.org/D28927

(cherry picked from commit 7972b985)