langgraph: separate prebuilt into a standalone package (#3589)

docs/docs/tutorials/plan-and-execute/plan-and-execute.ipynb

@@ -51,7 +51,7 @@
    "outputs": [],
    "source": [
     "%%capture --no-stderr\n",
-    "%pip install --quiet -U langgraph langchain-community langchain-openai tavily-python"
+    "%pip install --quiet -U langgraph langgraph-prebuilt langchain-community langchain-openai tavily-python"
    ]
   },
   {