Bump version to 5.3.0

• Diff: https://gitlab.com/gitlab-org/gitlab-qa/compare/v5.2.0...676330d90ce223e6cf1230f229680bdfad816c07

• Release notes:

### Reporter updates

- !410 Post identical failures as discussion comments

• 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:

  • Create a tag for the new release version.