docs: update pydantic comments -> callouts in tutorials (#1825)

docs/docs/tutorials/code_assistant/langgraph_code_assistant.ipynb

@@ -130,6 +130,19 @@
     "We will create a `code_gen_chain` w/ either OpenAI or Claude and test them here."
    ]
   },
+  {
+   "cell_type": "markdown",
+   "id": "95944645-35bc-4798-8a27-c262b245a74c",
+   "metadata": {},
+   "source": [
+    "<div class=\"admonition note\">\n",
+    "    <p class=\"admonition-title\">Using Pydantic with LangChain</p>\n",
+    "    <p>\n",
+    "        This notebook uses Pydantic v2 <code>BaseModel</code>, which requires <code>langchain-core >= 0.3</code>. Using <code>langchain-core < 0.3</code> will result in errors due to mixing of Pydantic v1 and v2 <code>BaseModels</code>.\n",
+    "    </p>\n",
+    "</div>"
+   ]
+  },
   {
    "cell_type": "code",
    "execution_count": 5,
@@ -150,7 +163,6 @@
    "source": [
     "from langchain_core.prompts import ChatPromptTemplate\n",
     "from langchain_openai import ChatOpenAI\n",
-    "# NOTE: you must use langchain-core >= 0.3 with Pydantic v2\n",
     "from pydantic import BaseModel, Field\n",
     "\n",
     "### OpenAI\n",