Upgrade Colab TF version to 1.13.1

Change-Id: I4be598d3e07f8207c9a201afd13a2269eca7619c

tutorials/vision/aiy_retrain_classification.ipynb

@@ -98,7 +98,7 @@
         "id": "XZBTCYDICwOG"
       },
       "source": [
-        "First, we need to remove the version of TensorFlow that's included with Google Colab by default, and replace it with TensorFlow 1.7, as required by the following training scripts."
+        "First, we need to remove the version of TensorFlow that's included with Google Colab by default, and replace it with TensorFlow 1.13.1, as required by the following training scripts."
       ]
     },
     {
@@ -118,7 +118,7 @@
         "id": "hLjaKNp9inlt"
       },
       "source": [
-        "! pip install -I absl-py==0.9 jupyter-client==6.1.5 tornado==5.1.0 folium==0.2.1 imgaug==0.2.5 tensorflow==1.7 tensorboard==1.7"
+        "! pip install -I absl-py==0.9 jupyter-client==6.1.5 tornado==5.1.0 folium==0.2.1 imgaug==0.2.5 tensorflow==1.13.1 tensorboard==1.13.1"
       ],
       "execution_count": null,
       "outputs": []
@@ -139,7 +139,7 @@
       },
       "source": [
         "import tensorflow as tf\n",
-        "assert tf.__version__.startswith('1.7')"
+        "assert tf.__version__.startswith('1.13.1')"
       ],
       "execution_count": null,
       "outputs": []