Bump version to 6.2.0

• Diff: https://gitlab.com/gitlab-org/gitlab-qa/compare/v6.1.3...1a23db099e0088a9d426e5b4c382663c9fb5b85b

• Release notes:

  • Remove the ce:docker and ee:docker jobs as they're not needed anymore :: Rémy Coutable
  • Merge branch 'remove-docker-jobs' into 'master' :: Dan Davison
  • Allow passthrough of DEPLOY_VERSION :: ddavison
  • Merge branch 'passthrough-deploy-version' into 'master' :: Dan Davison
  • Bump version to 6.2.0 :: ddavison

Other changes (CI, backstage)

• !530 (merged) Remove the ce:docker and ee:docker jobs as they're not needed anymore
• !531 (merged) Allow passthrough of DEPLOY_VERSION

- Checklist before merging:
  - [x] Diff link is up-to-date.
  - [x] Based on the diff, `lib/gitlab/qa/version.rb` is updated, according to [SemVer](https://semver.org).
  - [x] Release notes are accurate.

- Checklist after merging:
  - [ ] [Create a tag for the new release version](docs/release_process.md#how-to).