[Kickoff] Increase Kickoff information label readability

Summary: This patch vertically centers the information label (infolabel) that appears once a user hovers/runs over their username with their mouse as well as increases its opacity in favor of better readability.

Test Plan:
Before and after

{F6521485}

Reviewers: ngraham, #vdg, #plasma, GB_2

Reviewed By: #vdg, GB_2

Subscribers: abetts, GB_2, plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D17934