docs: remove mentions of pydantic_v1 in tutorials (#1709)

docs/docs/tutorials/rag/langgraph_adaptive_rag.ipynb

@@ -169,8 +169,10 @@
     "from typing import Literal\n",
     "\n",
     "from langchain_core.prompts import ChatPromptTemplate\n",
-    "from langchain_core.pydantic_v1 import BaseModel, Field\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",
     "\n",
     "\n",
     "# Data model\n",
@@ -922,7 +924,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.11.8"
+   "version": "3.11.9"
   }
  },
  "nbformat": 4,