readme: use `gitlab-ci` as the prefix in the container names of quickstart
readme: use `gitlab-ci` as the prefix in the container names of quickstart

sameersbn/docker-gitlab-ci,adiferd/docker-gitlab-ci,youhong316/docker-gitlab-ci,sameersbn/docker-gitlab-ci,youhong316/docker-gitlab-ci,bboehmke/docker-gitlab-ci,adiferd/docker-gitlab-ci,bboehmke/docker-gitlab-ci