seccomp rule documentation needs an update

[atombrella]

I couldn't find the file to edit for this text:
https://kubesec.io/basics/metadata-annotations-seccomp-security-alpha-kubernetes-io-pod/

This will result in a deprecation warning on currently support Kubernetes platforms. You've even updated the schema definition in #315

Could you please reflect this:
https://kubernetes.io/docs/tutorials/security/seccomp/#create-a-pod-that-uses-the-container-runtime-default-seccomp-profile

[atombrella]

You may also want to update (or add new) test assets for this:

https://github.com/controlplaneio/kubesec/blob/master/test/asset/score-0-pod-seccomp-non-unconfined.yml
https://github.com/controlplaneio/kubesec/blob/master/test/asset/score-0-pod-seccomp-unconfined.yml