Fix dataset path in Perceptron notebook

lessons/3-NeuralNetworks/03-Perceptron/Perceptron.ipynb

@@ -762,7 +762,7 @@
     "# !wget https://github.com/microsoft/AI-For-Beginners/raw/main/data/mnist.pkl.gz?raw=true\n",
     "# In this case correct the link to the dataset below as well.\n",
     "\n",
-    "with gzip.open('../../data/mnist.pkl.gz', 'rb') as mnist_pickle:\n",
+    "with gzip.open('../../../data/mnist.pkl.gz', 'rb') as mnist_pickle:\n",
     "    MNIST = pickle.load(mnist_pickle, encoding='latin1')"
    ]
   },
@@ -1203,4 +1203,4 @@
  },
  "nbformat": 4,
  "nbformat_minor": 2
-}
+}