[Notifications] Don't take updated time into account for sorting

Authored by broulik on May 18 2020, 2:58 PM.

Description

[Notifications] Don't take updated time into account for sorting

Notification spec says, when replacing a notification:

The server must atomically (ie with no flicker or other visual cues) replace the given notification with this one.

Notifications shifting about is a "visual cue".

Differential Revision: https://phabricator.kde.org/D29771