Bump version to 7.16.0

• Diff: v7.15.1...b60c3734

• Release notes:

### Other changes (CI, backstage)

- !806 Refactor reporting script

• 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.