Bump version to 6.22.1

• Diff: https://gitlab.com/gitlab-org/gitlab-qa/compare/v6.22.0...5a5e3156788cc5a6c736acda04eb97b473f9e081

• Release notes:

### Fixes

- !660 Fix issue when generating test session report where exception['message_lines'] is a String

• 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.