update langchain's api (#1745)

As ```chain.run()``` will be removed in langchain 0.2.0, it needs be
replaced with ```chain.invoke()```

Author: openvino-dev-samples

notebooks/254-llm-chatbot/254-rag-chatbot.ipynb

@@ -1346,7 +1346,7 @@
     "    stream_complete = Event()\n",
     "\n",
     "    def infer(question):\n",
-    "        rag_chain.run(question)\n",
+    "        rag_chain.invoke(question)\n",
     "        stream_complete.set()\n",
     "\n",
     "    t1 = Thread(target=infer, args=(history[-1][0],))\n",