Twenty Fifteen: pinching to zoom in on landscape on iPads is breaking the layout with the sticky sidebar. Providing a one-column view on those screens looks good and will likely prevent other bugs we don't even know about.

Props iamtakashi, fixes #30366.




git-svn-id: https://develop.svn.wordpress.org/trunk@30565 602fd350-edb4-49c9-b593-d223f7449a82