Bump version to 7.7.2

• Diff: https://gitlab.com/gitlab-org/gitlab-qa/compare/v7.7.1...39db55ec0067366561865cee7bcc36fdce25a1f8

• Release notes:

### Fixes

- !743 Update obsolete gitaly cluster config.

• 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.