Machine ID: Modify docs to use Machine ID helm chart

[strideynet]

Applies To

• https://goteleport.com/docs/enroll-resources/machine-id/deployment/kubernetes/
• https://goteleport.com/docs/admin-guides/access-controls/access-request-plugins/ssh-approval-slack/

Details

Following #44615 and #46353, we now have a Machine ID helm chart that can integrate with some of the access plugin charts. We should update the Machine ID and access plugin documentation to reflect this.

[stevenGravy]

Another option is using a Kubernetes job/cronjob that requires a machine-id access for say a database access or external k8s call. This would be a good example to have.