Update changelog

Author: xrmx

CHANGELOG.md

@@ -17,6 +17,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   ([#4270](https://github.com/open-telemetry/opentelemetry-python/pull/4270))
 - api: fix logging of duplicate EventLogger setup warning
   ([#4299](https://github.com/open-telemetry/opentelemetry-python/pull/4299))
+- sdk: fix serialization of logs severity_number field to int
+  ([#4324](https://github.com/open-telemetry/opentelemetry-python/pull/4324))
 
 ## Version 1.28.0/0.49b0 (2024-11-05)