Resolve "In GDK Kubernetes Agents docs still points to old config location"

What does this Merge Request do?

See

gitlab-org/cluster-integration/gitlab-agent!81 (merged)

and

gitlab-org/cluster-integration/gitlab-agent!61 (merged)

Merge Request checklist

• Tests added for new functionality. If not, please raise Issue to follow-up.
• This change is backward compatible. If not, please include steps to communicate to our users.
• Documentation added/updated, if needed.
• gdk doctor test added, if needed.

Closes #1074 (closed)