Update CHANGELOG.md

Author: xrmx

CHANGELOG.md

@@ -8,7 +8,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ## Unreleased
 
 - Add missing Prometheus exporter documentation
-  ([#4339](https://github.com/open-telemetry/opentelemetry-python/pull/4339))
+  ([#4485](https://github.com/open-telemetry/opentelemetry-python/pull/4485))
 - Fix user agent in OTLP HTTP metrics exporter
   ([#4475](https://github.com/open-telemetry/opentelemetry-python/pull/4475))
 - Improve performance of baggage operations