Fix NoMethodError when checking if ActionList::Dividers are active

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What are you trying to accomplish?

This change adds an active? method to ActionList::Divider. This is necessary so all types of item implement the same interface.

For additional background, the items slot on ActionList is polymorphic, i.e. allows multiple kinds of item. Currently supported items are 1) regular 'ol items, 2) avatar items, and 3) dividers. Both regular and avatar items define active?, but Divider does not. In at least one place we iterate over all items, attempting to call active? on each of them. If one is a Divider, Ruby raises a NoMethodError.

Integration

No changes necessary in production.

Risk Assessment

• Low risk the change is small, highly observable, and easily rolled back.
• Medium risk changes that are isolated, reduced in scope or could impact few users. The change will not impact library availability.
• High risk changes are those that could impact customers and SLOs, low or no test coverage, low observability, or slow to rollback.

Accessibility

• No new axe scan violation - This change does not introduce any new axe scan violations.

Merge checklist

• Added/updated tests
  - [ ] Added/updated documentation
  - [ ] Added/updated previews (Lookbook)
  - [ ] Tested in Chrome
  - [ ] Tested in Firefox
  - [ ] Tested in Safari
  - [ ] Tested in Edge

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🦋 Changeset detected

Latest commit: d5511b0

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@primer/view-components	Patch

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