Set default border value in all places

Summary:
The comment says this should match the default border setting in Breeze. Unfortunately it already doesn't. This patch makes it match the new border size in {D13481}.

Depends on D13481

Reviewers: #breeze, abetts

Reviewed By: abetts

Subscribers: abetts, plasma-devel

Tags: #plasma

Maniphest Tasks: T8707

Differential Revision: https://phabricator.kde.org/D13278