[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