Hero a11y Updates

[JoshBowdenConcepts]

Summary

A collection of changes requested from the a11y sign off review.

List of notable changes:

• removed aria-labeledby and id from the Hero component header because it was unnecessary
• removed br from the heading in the codespace story because it is inacessible

What should reviewers focus on?

• Making sure the Stories function correctly and reflect the requested changes in the a11y sign-off issue

Steps to test:

1. Open the Hero component in CI-deployed preview environment
2. Go to all stories in Storybook and on primer.style
3. Verify that each story behaves as expected

Contributor checklist:

• [ ] All new and existing CI checks pass
• [ ] Tests prove that the feature works and covers both happy and unhappy paths
• [ ] Any drop in coverage, breaking changes or regressions have been documented above
• [ ] New visual snapshots have been generated / updated for any UI changes
• [ ] All developer debugging and non-functional logging has been removed
• [ ] Related issues have been referenced in the PR description

Reviewer checklist:

• [ ] Check that pull request and proposed changes adhere to our contribution guidelines and code of conduct
• [ ] Check that tests prove the feature works and covers both happy and unhappy paths
• [ ] Check that there aren't other open Pull Requests for the same update/change

Links:

• closes https://github.com/github/primer/issues/1666