Update CHANGELOG.md

Author: xrmx

CHANGELOG.md

@@ -6,6 +6,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## Unreleased
+
 - Add `attributes` field in `metrics.get_meter` wrapper function
   ([#4364](https://github.com/open-telemetry/opentelemetry-python/pull/4364))