Correcting the device proportions on the Twenty Fourteen screenshot; see #26387.

git-svn-id: https://develop.svn.wordpress.org/trunk@26790 602fd350-edb4-49c9-b593-d223f7449a82
Minor adjustments to the Twenty Fourteen screenshot on the About page. See #26387.

git-svn-id: https://develop.svn.wordpress.org/trunk@26791 602fd350-edb4-49c9-b593-d223f7449a82