Documentation improvement: add missing period (#3754)

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.

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**Checklist (pre-PR):**

* [x] I have read the CLA Document and hereby sign the CLA.
* [x] I reviewed the “Contributing” markdown file for this project.

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

Co-authored-by: Eric Traut <etraut@openai.com>

Author: HarrisMBrad

CHANGELOG.md

@@ -1 +1 @@
-The changelog can be found on the [releases page](https://github.com/openai/codex/releases)
+The changelog can be found on the [releases page](https://github.com/openai/codex/releases).