Jetpack: Update language files for 2.8

See: http://translate.wordpress.com/projects/jetpack/
See: https://github.com/Automattic/jetpack/commit/f0a61ba84aa0506635a62e2cb83f96c435dcbaa7


git-svn-id: https://plugins.svn.wordpress.org/jetpack/trunk@848378 b8457f37-d9ea-0310-8a92-e5e31aec5664