Update graph-NSL tutorial after renaming of the graph_loss metric name in NSL v1.3.0.

PiperOrigin-RevId: 324266753

Author: arjung

g3doc/tutorials/graph_keras_lstm_imdb.ipynb

@@ -1381,7 +1381,7 @@
         "acc = graph_reg_history_dict['accuracy']\n",
         "val_acc = graph_reg_history_dict['val_accuracy']\n",
         "loss = graph_reg_history_dict['loss']\n",
-        "graph_loss = graph_reg_history_dict['graph_loss']\n",
+        "graph_loss = graph_reg_history_dict['scaled_graph_loss']\n",
         "val_loss = graph_reg_history_dict['val_loss']\n",
         "\n",
         "epochs = range(1, len(acc) + 1)\n",