[Kicker, Kickoff & Dash] Change labels to match SDDM theme labels
Summary: This patch follows patch D19458 and applies the same label changes to Kicker/Kickoff/Dash.
Reviewers: VDG, ngraham
Reviewed By: VDG, ngraham
Subscribers: plasma-devel
Tags: Plasma
Differential Revision: https://phabricator.kde.org/D19459