update CHANGELOG.md

Author: herin049

CHANGELOG.md

@@ -49,6 +49,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Refactor unit tests to allow for population of the random trace id flag in the `traceparent` header
   ([#4030](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/4030))
 - `opentelemetry-instrumentation-mysqlclient`: Update unit tests to properly validate trace context trace flag values.
+  ([#4560](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/4560))
 
 ### Breaking changes