fix: pin langgraph <= 1.1.6 to avoid GraphCallbackHandler breaking change

Author: shuwpan

instrumentation-genai/opentelemetry-instrumentation-langchain/pyproject.toml

@@ -35,6 +35,7 @@ instruments = ["langchain >= 0.3.21"]
 test = [
   "langchain-core >= 1.0.0",
   "langchain-openai >= 1.0.0",
+  "langgraph <= 1.1.6",
   "pytest-recording >= 0.13.0",
   "vcrpy >= 7.0.0",
   "pyyaml >= 6.0.0",