[notifications] Remove unread counter, use icon instead
Summary:
Text inside a small circle has a lot of problems with fitting in there
and being properly aligned.
Test Plan:
Breeze:
Breeze (with D23019):
Air:
Oxygen:
Reviewers: VDG, Plasma, ngraham
Reviewed By: VDG, ngraham
Subscribers: ngraham, broulik, plasma-devel
Tags: Plasma
Differential Revision: https://phabricator.kde.org/D23018