ADd changelog

Author: xrmx

CHANGELOG.md

@@ -20,6 +20,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 
+- `opentelemetry-instrumentation-httpx`: instrument_client is a static method again
+  ([#3003](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/3003))
+
 ### Breaking changes
 
 - `opentelemetry-instrumentation-sqlalchemy` teach instruments version