Documentation improvement: add missing period

[HarrisMBrad]

Pull request template, minimal:

---

What?

Minor change (low-hanging fruit).

Why?

To improve code quality or documentation with minimal risk and effort.

How?

Edited directly via VSCode Editor.

---

Checklist (pre-PR):

• I have read the CLA Document and hereby sign the CLA.
• I reviewed the “Contributing” markdown file for this project.

This template meets standard external (non-OpenAI) PR requirements and signals compliance for maintainers.

[github-actions]

All contributors have signed the CLA ✍️ ✅
_{Posted by the CLA Assistant Lite bot.}

[HarrisMBrad]

I have read the CLA Document and I hereby sign the CLA

[HarrisMBrad]

recheck

[etraut-openai]

Thanks for the contribution, and apologies for the slow response. We've received many PRs, and we haven't had the bandwidth on the codex team to review all of them.