docs: fixed indentation (#4078)

"Copy the clipboard" doesn't return valid Python code.

docs/docs/tutorials/introduction.ipynb

@@ -279,7 +279,6 @@
     "        if user_input.lower() in [\"quit\", \"exit\", \"q\"]:\n",
     "            print(\"Goodbye!\")\n",
     "            break\n",
-    "\n",
     "        stream_graph_updates(user_input)\n",
     "    except:\n",
     "        # fallback if input() is not available\n",