add PR to changelog

Author: joshschltelus

Diff for: CHANGELOG.md

@@ -20,6 +20,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   ([#2573](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/2573))
 - `opentelemetry-instrumentation-confluent-kafka` Add support for version 2.4.0 of confluent_kafka
   ([#2616](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/2616))
+- `opentelemetry-instrumentation-confluent-kafka` Add support for produce purge
+  ([#2638](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/2638))
 
 ### Breaking changes