Update instrumentation-genai/opentelemetry-instrumentation-openai-v2/CHANGELOG.md

Author: xrmx

instrumentation-genai/opentelemetry-instrumentation-openai-v2/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
+
 - Fix `AttributeError` when handling `LegacyAPIResponse` (from `with_raw_response`)
   ([#4002](https://github.com/open-telemetry/opentelemetry-python-contrib/issues/4002))