Fix (temporarily?) the spacing between the uploader buttons on the dashboard,...

Fix (temporarily?) the spacing between the uploader buttons on the dashboard, props SergeyBiryukov and andrewryno, see #17144

git-svn-id: https://core.svn.wordpress.org/trunk@18553 1a063a9b-81f0-0310-95a4-ce76da25c4cd