KateSessionManager: Sort the jump list actions by time not alphabetical

Summary:
    This is certainly only a notable benefit when there are more sessions
    available than the limited count of entries. The drawback is that this
    way the (supposed expensive) update takes more often in effect.

Reviewers: #kate, cullmann

Reviewed By: #kate, cullmann

Subscribers: cullmann, kwrite-devel, #kate

Tags: #kate

Differential Revision: https://phabricator.kde.org/D16645