authYubiKey: Remove deprecated uses of split().
authYubiKey: Remove deprecated uses of split().

We should probably update this library to the latest version, but that
must wait until we can test the changes. This should at least fix the
deprecated-function warnings that PHP produces.

Thanks to Thijs Kinkhorst for providing this patch.

simplesamlphp/saml2,cb8/saml2,ArtemTeleshev/php-saml2,madmatt/saml2,newmen/saml2,sitya/saml2,sgomez/saml2