Merge branch 'renovate/to-be-continuous-docker-2.x' into 'master'

Update dependency to-be-continuous/docker to v2.3.0

See merge request to-be-continuous/tools/tracking!10

.gitlab-ci.yml

 include:
  - project: 'to-be-continuous/docker'
-   ref: '2.2.0'
+   ref: '2.3.0'
    file: '/templates/gitlab-ci-docker.yml'
  - project: 'to-be-continuous/golang'
    ref: '2.1.2'