Remove outdated code from Chat VectorDB QA example (#1670)

docs/modules/chat/examples/vector_db_qa_with_sources.ipynb

@@ -166,28 +166,6 @@
     "chain({\"question\": \"What did the president say about Justice Breyer\"}, return_only_outputs=True)"
    ]
   },
-  {
-   "cell_type": "code",
-   "execution_count": 11,
-   "id": "c91fdc8a",
-   "metadata": {},
-   "outputs": [
-    {
-     "data": {
-      "text/plain": [
-       "{'answer': ' The president honored Justice Stephen Breyer for his service.\\n',\n",
-       " 'sources': '30-pl'}"
-      ]
-     },
-     "execution_count": 11,
-     "metadata": {},
-     "output_type": "execute_result"
-    }
-   ],
-   "source": [
-    "qa({\"question\": \"What did the president say about Justice Breyer\"}, return_only_outputs=True)"
-   ]
-  }
  ],
  "metadata": {
   "kernelspec": {