[RFC] Fix Display Configuration icon margins

Summary:
The icon's old margins were too large, causing it to stick out.

BUG: 400087
FIXED-IN: 5.66

Test Plan:

Reviewers: VDG, ndavis

Reviewed By: VDG, ndavis

Subscribers: trickyricky26, kde-frameworks-devel

Tags: Frameworks

Differential Revision: https://phabricator.kde.org/D25296