Simplify code in the paintEvent

Summary:
Simplifies the code in the paintEvent related to the
placement of the colored arcs.

Test Plan: Run blinken, verified that the arcs are in the correct place

Reviewers: aacid

Reviewed By: aacid

Subscribers: kde-edu

Tags: KDE Edu

Differential Revision: https://phabricator.kde.org/D15624