Update container linking documentation

As of 1.3 `docker ps` no longer shows links between containers.
This updates the documentation to reflect that change.

    sudo docker docker inspect -f "{{ .HostConfig.Links }}" web

Signed-off-by: Philipp Weissensteiner <mail@philippweissensteiner.com>
Merge pull request #8682 from wpp/update_linking_documentation

Update linking documentation