Remove overlay anchored position background

[keithamus]

Reviewers: By approving this Pull Request you are approving the code change, as well as its deployment and mitigation plans.
Please read this description carefully. If you feel there is anything unclear or missing, please ask for updates.

What are you trying to accomplish?

Fix the visual bug described in https://github.com/github/primer/issues/2643.

Screenshots

Before:

After:

Integration

List the issues that this change affects.

Closes https://github.com/github/primer/issues/2643

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.

What approach did you choose and why?

Add background:none to anchored-position.

Anything you want to highlight for special attention from reviewers?

N/A

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

Take a look at the What we look for in reviews section of the contributing guidelines for more information on how we review PRs.

[changeset-bot]

🦋 Changeset detected

Latest commit: a41e645

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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[github-actions]

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[langermank]

Thank you!