Fix Dvorak support

This removes the check that requires the OTP of the response to match that of the request. The Yubico API does Dvorak to QWERTY conversion which can make this fail. Obviously, this could also be resolved by doing the conversion in the library before hitting the endpoint, but the downside is that we wouldn't get other layout support for free (if Yubico began supporting Colemak, the library would also reject these until proper conversion had been implemented).