Add a comment about sklearn.metrics.plot_confusion_matrix, fixes ageron#142

Author: ageron

03_classification.ipynb

@@ -1453,6 +1453,7 @@
    "metadata": {},
    "outputs": [],
    "source": [
+    "# since sklearn 0.22, you can use sklearn.metrics.plot_confusion_matrix()\n",
     "def plot_confusion_matrix(matrix):\n",
     "    \"\"\"If you prefer color and a colorbar\"\"\"\n",
     "    fig = plt.figure(figsize=(8,8))\n",