Consider removing @DockerRequired

[jasondlee]

The @DockerRequired annotation is likely not needed. The point of this module is to support lifecycle control and injection of Testcontainer instances, so Docker (or Podman) being required is implied. We should be able to remove this annotation, then, and perform any container-readiness checks during the injection handling.

[jamezp]

The one place, and maybe there is a workaround, where the annotation is beneficial is to fail-fast. However, I'm not sure how critical that is.