remove atomic support because reached end of live (#5783)

README.md

docs/_sidebar.md

docs/atomic.md

roles/bootstrap-os/tasks/bootstrap-centos.yml

roles/bootstrap-os/tasks/bootstrap-fedora.yml

roles/container-engine/containerd/tasks/containerd_repo.yml

roles/container-engine/containerd/tasks/main.yml

roles/container-engine/cri-o/tasks/main.yaml

roles/container-engine/docker/tasks/main.yml

roles/etcd/meta/main.yml

roles/kubernetes/preinstall/meta/main.yml

roles/kubernetes/preinstall/tasks/0040-set_facts.yml

roles/kubernetes/preinstall/tasks/0070-system-packages.yml

roles/kubespray-defaults/defaults/main.yaml