Docs feedback: GitLab CI DIND DOCKER_HOST using different port

Doc: https://docs.gitlab.com/ee/ci/docker/using_docker_build.html

After setting it up, docker started successfully but printed

time="2019-08-05T10:25:08.716633313Z" level=info msg="API listen on [::]:2376"

The readme mentions DOCKER_HOST: tcp://docker:2375, but that doesn't work