update link to yubikey docs

[nirik]

Currently (in fas2) https://admin.fedoraproject.org/accounts/yubikey

has a link to http://www.yubico.com/files/YubiKey_manual-2.0.pdf but that no longer exists.
Probibly we should point it to our wiki or a higher level doc...
https://www.yubico.com/wp-content/uploads/2015/03/YubiKeyManual_v3.4.pdf works for now, but isn't good long term most likely.

See https://fedorahosted.org/fedora-infrastructure/ticket/5451 for downstream report.

[sijis]

I was going to try and put in a PR for this as it seemed easy. In doing so, this seems to have been updated in this commit: b8c7bec
Also, based on their releases, its included in 0.14.0 release.

[laxathom]

Closed as resolved.