Fix typecheck in langchain instrumentation (#3773)

* fix typecheck

* fix ruff and added changelog

* added lambda list

* Update instrumentation-genai/opentelemetry-instrumentation-langchain/CHANGELOG.md

---------

Co-authored-by: Riccardo Magliocchetti <[email protected]>

Author: wrisa

instrumentation-genai/opentelemetry-instrumentation-langchain/src/opentelemetry/instrumentation/langchain/span_manager.py

@@ -31,7 +31,7 @@
 @dataclass
 class _SpanState:
     span: Span
-    children: List[UUID] = field(default_factory=list)
+    children: List[UUID] = field(default_factory=lambda: list())
 
 
 class _SpanManager: