Prepare 1.6.10 release (#512)

## Summary

- Add a `1.6.10` changelog entry for Python 3.13 support
- Bump `unstructured_inference.__version__` to `1.6.10`

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> **Low Risk**
> Low risk release metadata update only: bumps the library version and
adds a changelog entry; no runtime logic changes.
> 
> **Overview**
> Prepares the `1.6.10` release by adding a `1.6.10` entry to
`CHANGELOG.md` noting **Python 3.13 support**.
> 
> Bumps `unstructured_inference.__version__` from `1.6.9` to `1.6.10`.
> 
> <sup>Reviewed by [Cursor Bugbot](https://cursor.com/bugbot) for commit
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code reviews on this repo. Configure
[here](https://www.cursor.com/dashboard/bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

Author: CyMule

CHANGELOG.md

@@ -1,3 +1,8 @@
+## 1.6.10
+
+### Enhancement
+- Add Python 3.13 support.
+
 ## 1.6.9
 
 ### Enhancement

unstructured_inference/__version__.py

@@ -1 +1 @@
-__version__ = "1.6.9"  # pragma: no cover
+__version__ = "1.6.10"  # pragma: no cover