build(config.yml): pin langfuse version

.circleci/config.yml

@@ -35,7 +35,7 @@ jobs:
             pip install "aioboto3==12.3.0"
             pip install langchain
             pip install lunary==0.2.5
-            pip install "langfuse>=2.0.0"
+            pip install "langfuse==2.7.3"
             pip install numpydoc
             pip install traceloop-sdk==0.0.69
             pip install openai