Remove all remnants of outdated notification system
Summary:
The notification system is not used anywhere
anymore. There is no single emit of
newNotification within Elisa.
If new notifications are added to Elisa, they
should use a PassiveNotification from Kirigami.
More ui cleanup will follow later.
Reviewers: mgallien, ngraham
Reviewed By: mgallien, ngraham
Tags: Elisa
Differential Revision: https://phabricator.kde.org/D23223