Adjusts zIndexes to be not-as-absurd as before, in the process moving the modal below the plupload flash shims (which do not have customizable zIndexes or classes, sadly). fixes #22441, see #22446, #21390. git-svn-id: http://core.svn.wordpress.org/trunk@22611 1a063a9b-81f0-0310-95a4-ce76da25c4cd