Themes: Remove a now defunct CSS class, .feature-container, which is no longer in use after r26141. See #25948


git-svn-id: https://develop.svn.wordpress.org/trunk@26465 602fd350-edb4-49c9-b593-d223f7449a82
Themes: Remove the Tabs from the header of the Add New Theme page. Fixes #26310


git-svn-id: https://develop.svn.wordpress.org/trunk@26466 602fd350-edb4-49c9-b593-d223f7449a82