Amend comment to task 4 of notebook 01

Author: ma595

exercises/01_penguin_classification.ipynb

@@ -374,7 +374,7 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "# Complete __len__() and __getitem__() functions\n",
+    "# Complete __getitem__() function\n",
     "# See Task 4 ``TODOs`` in PenguinDataset class.\n",
     "\n",
     "# Create train_set\n",