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

docs/docs/how-tos/persistence_postgres.ipynb

@@ -44,8 +44,7 @@
     "...\n",
     "```\n",
     "\n",
-    "!!! info \"Setup\"",
-    "\n",
+    "!!! info \"Setup\"\n",
     "    You need to run `.setup()` once on your checkpointer to initialize the database before you can use it."
    ]
   },
@@ -70,7 +69,7 @@
    "outputs": [],
    "source": [
     "%%capture --no-stderr\n",
-    "%pip install -U psycopg psycopg-pool langgraph langgraph-checkpoint-postgres"
+    "%pip install -U psycopg psycopg-pool langgraph langgraph-prebuilt langgraph-checkpoint-postgres"
    ]
   },
   {