Bump VERSION to 4.9.0

• Diff: v4.8.1...0aa4a4a0

• Release notes:

### New scenarios and scenario updates

- !321 Remove unneeded network arg from geo scenario

### Fixes

- !314 Update docker dind service to 19.03.0-dind

### Doc changes

- !319 Improve the Release process a bit

### Other changes (CI, backstage)

- !320 Add logic to include empty tests
- !322 Update minio component with explanatory comment about hardcoded secrets

• Checklist before merging:

  • Diff link is up-to-date.
  • Based on the diff, lib/gitlab/qa/version.rb is updated, according to SemVer.
  • Release notes are accurate.

• Checklist after merging:

  • Create a tag for the new release version.