Fix ActionButton size
Summary: Its dimensions were cut in half by the change in largeSpacing introduced in 735da5da3ab5c66855b76efe69c9b239ed158b3b.
Reviewers: Kirigami, mart
Reviewed By: Kirigami, mart
Subscribers: ngraham, plasma-devel, Kirigami
Tags: Kirigami
Differential Revision: https://phabricator.kde.org/D11205