docs: note langchain v2 rename

Author: nagkumar91

instrumentation-genai/opentelemetry-instrumentation-langchain-v2/CHANGELOG.md

@@ -8,4 +8,6 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ## Unreleased
 
 - Added span support for genAI langchain llm invocation.
-  ([#3665](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/3665))
+  ([#3665](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/3665))
+- Renamed package directory to `opentelemetry-instrumentation-langchain-v2`.
+  ([#3873](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/3873))