Saner CSS for row actions - now we can just target `.row-actions` instead of both `.row-actions` and `.row-actions-visible`. CSS for `.row-actions-visible` remains for now due to usage in plugins. Visibility is controlled by toggling a `.visible` class. fixes #25403.

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git-svn-id: http://core.svn.wordpress.org/trunk@25509 1a063a9b-81f0-0310-95a4-ce76da25c4cd