doc updates (#1639)

---------

Co-authored-by: vbarda <vadym@langchain.dev>

examples/plan-and-execute/plan-and-execute.ipynb

@@ -83,19 +83,12 @@
    "id": "be2d7981-3737-4134-8bef-d00d18d4e91d",
    "metadata": {},
    "source": [
-    "Optionally, we can set API key for LangSmith tracing, which will give us best-in-class observability."
-   ]
-  },
-  {
-   "cell_type": "code",
-   "execution_count": 2,
-   "id": "01f460d1-f26f-47d1-ae76-de74d5d851de",
-   "metadata": {},
-   "outputs": [],
-   "source": [
-    "os.environ[\"LANGCHAIN_TRACING_V2\"] = \"true\"\n",
-    "_set_env(\"LANGCHAIN_API_KEY\")\n",
-    "os.environ[\"LANGCHAIN_PROJECT\"] = \"Plan-and-execute\""
+    "<div class=\"admonition tip\">\n",
+    "    <p class=\"admonition-title\">Set up <a href=\"https://smith.langchain.com\">LangSmith</a> for LangGraph development</p>\n",
+    "    <p style=\"padding-top: 5px;\">\n",
+    "        Sign up for LangSmith to quickly spot issues and improve the performance of your LangGraph projects. LangSmith lets you use trace data to debug, test, and monitor your LLM apps built with LangGraph — read more about how to get started <a href=\"https://docs.smith.langchain.com\">here</a>. \n",
+    "    </p>\n",
+    "</div>    "
    ]
   },
   {