Bump version to 7.2.1

• Diff: https://gitlab.com/gitlab-org/gitlab-qa/compare/v7.2.0...71661e058de0e7f13cf1b9f9e4f4b22225a1ccf0

• Release notes:

### Fixes

- !701 Removing the analysis lines on the mTLS test
- !702 Add Omnibus config for cloud license mode

• 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.