docs: fix assistants url at manage_assistants.md (#4993)

* docs: fix agent supervisor doc codes

* docs: fix assistants url at manage_assistants.md

docs/docs/tutorials/multi_agent/agent_supervisor.ipynb

@@ -54,7 +54,6 @@
     "    if not os.environ.get(var):\n",
     "        os.environ[var] = getpass.getpass(f\"Please provide your {var}\")\n",
     "\n",
-    "\n",
     "_set_if_undefined(\"OPENAI_API_KEY\")\n",
     "_set_if_undefined(\"TAVILY_API_KEY\")"
    ]
@@ -1369,6 +1368,14 @@
     "):\n",
     "    pretty_print_messages(chunk, last_message=True)"
    ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "6d3916d1-7de9-47c1-ae6f-80865b804e77",
+   "metadata": {},
+   "outputs": [],
+   "source": []
   }
  ],
  "metadata": {
@@ -1387,7 +1394,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.12.3"
+   "version": "3.12.10"
   }
  },
  "nbformat": 4,