Update Angelo's status from trainee maintainer to maintainer

Manager Justification

• The MRs reviewed by the candidate consistently make it through maintainer review without significant additionally required changes.
• The MRs authored by the candidate consistently make it through reviewer and maintainer review without significant required changes.

• Angelo(@agulina) is a Senior Frontend Engineer and has been working with the Fulfillment team for almost 2 years.
• Angelo have approved ~65 merge requests within the CustomersDot repository. Trainee FE maintainer (CustomersDot) - Angelo G... (gitlab-org/customers-gitlab-com#2523 - closed)
• Angelo have authored ~85 merge requests within the CustomersDot repository.

Before Merging (Manager Tasks)

• Mention the maintainers from the given specialty and ask them to provide feedback to the manager directly.
• Leave this merge request open for 1 week, to give the maintainers time to provide feedback.
• Ensure we have at least 2 approvals from existing maintainers.

Once This MR is Merged

1. Create an access request for maintainer access to gitlab-org/<project>.
2. Join the [at]frontend-maintainers slack group
3. Ask the maintainers in your group to invite you to any maintainer-specific meeting if one exists.
4. Let a maintainer add you to gitlab-org/maintainers/frontend
5. Announce it everywhere
6. Keep reviewing, start merging 🤘 😎 🤘