utils/shared_audits: allow subgroups in gitlab url

[cho-m]

• Have you followed the guidelines in our Contributing document?
• Have you checked to ensure there aren't other open Pull Requests for the same change?
• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your changes? Here's an example.
• Have you successfully run brew style with your changes locally?
• Have you successfully run brew typecheck with your changes locally?
• Have you successfully run brew tests with your changes locally?

---

To fix: https:/Homebrew/homebrew-core/actions/runs/10570029877/job/29283904401#step:3:38

Subgroups: https://docs.gitlab.com/ee/user/group/subgroups/

Extra characters: https://docs.gitlab.com/ee/user/reserved_names.html#limitations-on-usernames-project-and-group-names-and-slugs

---

The starting \w is a slightly shorter-to-type superset of [A-Za-z0-9] (#{Alnum}). Mainly to avoid [\w.-]+ matching unique /-/; however, not really needed as there should never be a URL with /-/-/

[MikeMcQuaid]

Thanks again @cho-m!