Delete unused fedora docker repo

roles/docker/vars/fedora-20.yml

----
-docker_kernel_min_version: '0'
-
-# versioning: docker-io itself is pinned at docker 1.5
-
-docker_package_info:
-  pkg_mgr: yum
-  pkgs:
-    - name: docker-io
-
-docker_repo_key_info:
-  pkg_key: ''
-  repo_keys: []
-
-docker_repo_info:
-  pkg_repo: ''
-  repos: []

roles/docker/vars/fedora.yml

----
-docker_kernel_min_version: '0'
-
-# https://docs.docker.com/engine/installation/linux/fedora/#install-from-a-package
-# https://download.docker.com/linux/fedora/7/x86_64/stable/
-# the package names below are guesses;
-# docs mention `sudo dnf config-manager --enable docker-ce-edge` for edge
-docker_versioned_pkg:
-  'latest': docker
-  '1.11': docker-1:1.11.2
-  '1.12': docker-1:1.12.6
-  '1.13': docker-1.13.1
-  '17.03': docker-17.03.1
-  'stable': docker-ce
-  'edge': docker-ce-edge
-
-docker_package_info:
-  pkg_mgr: dnf
-  pkgs:
-    - name: "{{ docker_versioned_pkg[docker_version | string] }}"
-
-docker_repo_key_info:
-  pkg_key: ''
-  repo_keys: []
-
-docker_repo_info:
-  pkg_repo: ''
-  repos: []