Bump version to 5.0.0

• Diff: https://gitlab.com/gitlab-org/gitlab-styles/compare/v4.3.0...b7bff46a78b8216f24be37eb9f8d1a70f1e6f975

• Release notes:

### New scenarios and scenario updates

- !49 Add line break detection for let_it_be.
- !50 Update rubocop and dependencies.
- !51 Configure new rubocop cops.
- !52 Upstream CodeReuse/ActiveRecord Cop from GitLab.

### Other changes (CI, backstage)

- !47 Modify release template for new labels.

• Checklist before merging:

  • Diff link is up-to-date.
  • Based on the diff, lib/gitlab/styles/version.rb is updated, according to SemVer.
  • Release notes are accurate.

• Checklist after merging:

  • Create a tag for the new release version.