Update the 'Retina Ready' screenshot on the about page to reflect version 3.5,...

Update the 'Retina Ready' screenshot on the about page to reflect version 3.5, Twenty Twelve, and such. It's the little things. props lessbloat. fixes #22455.



git-svn-id: https://core.svn.wordpress.org/trunk@23022 1a063a9b-81f0-0310-95a4-ce76da25c4cd