Fix alignment and borders of plugin/theme updates on the Updates screen.

Merges [26935] to the 3.8 branch.

props morganestes, ocean90.
see #26699.

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git-svn-id: http://core.svn.wordpress.org/branches/3.8@26819 1a063a9b-81f0-0310-95a4-ce76da25c4cd