That certification covered experience with enterprise components, like the Universal Control Plane (UCP) and Docker Trusted Registry (DTR). These all moved over to Mirantis. While they've rebranded the products, for some reason the certification itself has not been rebranded. However, it has little to do with Docker's OSS offerings, that remained with Docker Inc., other than being a shared based for the enterprise tooling. You're probably better off getting certified in the cloud you'll be supporting, and consider one of the Kubernetes certifications, unless you intend to support a Mirantis Enterprise project.