Updating .wp-dialog styling to match the new admin design. Fixes #26328, props SergeyBiryukov, Ocean90.


Built from https://develop.svn.wordpress.org/trunk@26528


git-svn-id: http://core.svn.wordpress.org/trunk@26421 1a063a9b-81f0-0310-95a4-ce76da25c4cd