Use current_user_can('manage_network_plugins') in validate_active_plugins() instead of is_super_admin().

props jdgrimes.
fixes #26068.

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Twenty Fourteen: fix JS lint errors in customizer.js file, see r26573.
Built from https://develop.svn.wordpress.org/trunk@26591


git-svn-id: http://core.svn.wordpress.org/trunk@26481 1a063a9b-81f0-0310-95a4-ce76da25c4cd