We're in the process of removing the Creative Commons and Answers searchplugins from the tree (bug 1068456). Note that Creative Commons is currently broken (bug 939804), and has been not working for a while. I sent an email to the dev-l10n mailing list over a year ago, not having received any reply or concern I'll move ahead and remove the reference to these plugins in your locale. Filing this bug for reference and better tracking.

https://hg.mozilla.org/releases/l10n/mozilla-beta/vi/rev/58fd5d615c46 https://hg.mozilla.org/releases/l10n/mozilla-aurora/vi/rev/58fd5d615c46 https://hg.mozilla.org/l10n-central/vi/rev/58fd5d615c46