About Page: Fix issue with overlapping images and text on IE11 and Edge 15.

Props Clorith, ryelle, afercia, la-geek, SergeyBiryukov.
See #42514.
Fixes #42545.

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git-svn-id: https://core.svn.wordpress.org/trunk@42011 1a063a9b-81f0-0310-95a4-ce76da25c4cd