`jcmturner/gokrb5` is no more maintained

https://github.com/jcmturner/gokrb5 is not maintained anymore.

It also contains a bug where if the Kafka server sends multiple authentication headers - the kerberos client will only read the first header to decide if it should use kerberos authentication or not.

Ideally, it should look for "Negotiate" in all the headers received. See https://github.com/jcmturner/gokrb5/blob/master/v8/spnego/http.go#L160