Bump version to 5.5.0

• Diff: v5.4.3...2ab98dc2

• Release notes:

### New reporting features

- !432 Add ability to update screenshot path in JUnit report file

### Other changes (CI, backstage)

- !433 Add docker jobs back

• 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.