Update Docker to 20.10 in our pipelines on CI/CD
It is time to update Docker to 20.10 on CI/CD of GitLab since:
1. Docker 20.10 was released in 2020-12, 17 months after 19.03: https://www.docker.com/blog/introducing-docker-engine-20-10/
2. GitLab Dependency Scanning does not allow us to use 19.03.0: https://docs.gitlab.com/ee/user/application_security/dependency_scanning/index.html
In most projects under `@gitlab-org` currently we are using 19.03.x on CI/CD through the projects under the group.
### TODOs for `gitlab-org/gitlab` projects (as of 2021-04-09)
- [ ] gitlab-org/gitlab (gitlab-org/gitlab-foss)
https://sourcegraph.com/search?q=repo:gitlab.com/gitlab-org/gitlab%24+docker:19.03&patternType=literal&case=yes
### TODOs for non-`gitlab-org/gitlab` projects (as of 2021-04-09)
- [x] gitlab-org/cluster-integration/auto-deploy-image#163
- [x] gitlab-org/security-products/dast!400 (issue: gitlab-org/gitlab#323454)
- [ ] gitlab-org/ci-cd/docker-machine
- [ ] gitlab-org/ci-cd/tests/dind-image-tests
- [x] gitlab-org/cloud-deploy!33 (gitlab-org/cloud-deploy#18)
- [x] gitlab-org/gitlab-qa!664 (gitlab-org/gitlab-qa#630)
https://sourcegraph.com/search?q=repo:gitlab.com/gitlab-org+docker:19.03+-repo:%5Egitlab%5C.com/gitlab-org/gitlab%24+-repo:%5Egitlab%5C.com/gitlab-org/gitlab-foss%24+&patternType=literal&case=yes
### Related epics
- &5109
### References
- https://sourcegraph.com/search?q=repo:gitlab.com/gitlab-org+docker:19.03&patternType=literal&case=yes
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