update changelog

Author: aabmass

Diff for: CHANGELOG.md

@@ -6,6 +6,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased](https://github.com/open-telemetry/opentelemetry-python/compare/v1.5.0-0.24b0...HEAD)
 
+- Make Measurement a concrete class
+  ([#2153](https://github.com/open-telemetry/opentelemetry-python/pull/2153))
 - Add metrics API
   ([#1887](https://github.com/open-telemetry/opentelemetry-python/pull/1887))
 - `opentelemetry-semantic-conventions` Update to semantic conventions v1.6.1