chore: update minimum Code Ocean platform version to 3.9.0 in CHANGELOG

Author: zvikagart

CHANGELOG.md

@@ -3,6 +3,7 @@ CHANGELOG
 
 ## 0.10.0 (2025-09-01)
 - [#54](https://github.com/codeocean/codeocean-sdk-python/pull/54) feat: Code Ocean version 3.9 functionality
+- **Minimum Code Ocean platform version updated to `3.9.0`.** 
 
 ## 0.9.1 (2025-08-29)
 - [#56](https://github.com/codeocean/codeocean-sdk-python/pull/56) fix: update query description in search APIs