update changelog

Signed-off-by: Alex Boten <[email protected]>

Author: codeboten

CHANGELOG.md

@@ -32,6 +32,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   ([#4406](https://github.com/open-telemetry/opentelemetry-python/pull/4406))
 - Fix env var error message for TraceLimits/SpanLimits
   ([#4458](https://github.com/open-telemetry/opentelemetry-python/pull/4458))
+- Fix user agent in OTLP HTTP metrics exporter
+  ([#4475](https://github.com/open-telemetry/opentelemetry-python/pull/4475))
 
 ## Version 1.30.0/0.51b0 (2025-02-03)