Update CHANGELOG.md for user agent fix

Author: emdneto

CHANGELOG.md

@@ -7,6 +7,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## Unreleased
 
+- Fix user agent in OTLP HTTP metrics exporter
+  ([#4475](https://github.com/open-telemetry/opentelemetry-python/pull/4475))
+
 ## Version 1.31.0/0.52b0 (2025-03-12)
 
 - semantic-conventions: Bump to 1.31.0
@@ -38,8 +41,6 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   ([#4458](https://github.com/open-telemetry/opentelemetry-python/pull/4458))
 - pylint-ci updated python version to 3.13
   ([#4450](https://github.com/open-telemetry/opentelemetry-python/pull/4450))
-- 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)