Admin Reskin: Correct alignment for spinners across the admin.

Follow-up to [61646].

Props wildworks, anupkankale, shailu25, gaurangsondagar, jadavsanjay, SergeyBiryukov.
Fixes #65131.

git-svn-id: https://develop.svn.wordpress.org/trunk@62291 602fd350-edb4-49c9-b593-d223f7449a82