Add changelog

Author: xrmx

CHANGELOG.md

@@ -34,6 +34,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   ([#2922](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/2922))
 - `opentelemetry-instrumentation-celery` Don't detach context without a None token
   ([#2927](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/2927))
+- `opentelemetry-exporter-prometheus-remote-write`: sort labels before exporting
+  ([#2940](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/2940))
 
 ### Breaking changes