Update version to 9.0.0

• Diff: v8.15.3...32cc24e3

• Release notes:

### Breaking change

- !1125 Set license mode via GitLab component only

• 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:

  • Update the release notes for the newly created tag.