Bump version to 7.3.1

• Diff: https://gitlab.com/gitlab-org/gitlab-qa/compare/v7.3.0...32064e6634867995d211e538d856adce2087f425

• Release notes:

### Fixes

- !708 Update generate allure report env var name

### New scenarios and scenario updates

- !650 Adding SSL check for clients

### Other changes (CI, backstage)

- !707 Update .gitlab-ci.yml to include a Registry job

• 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.