fix(docs): json_mode -> json_schema (#32993)

Author: mdrxy

docs/docs/how_to/structured_output.ipynb

@@ -668,7 +668,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 14,
+   "execution_count": null,
    "id": "df0370e3",
    "metadata": {},
    "outputs": [
@@ -685,7 +685,7 @@
     }
    ],
    "source": [
-    "structured_llm = llm.with_structured_output(None, method=\"json_mode\")\n",
+    "structured_llm = llm.with_structured_output(None, method=\"json_schema\")\n",
     "\n",
     "structured_llm.invoke(\n",
     "    \"Tell me a joke about cats, respond in JSON with `setup` and `punchline` keys\"\n",