Correct axis labelling in chapter two

Author: NathanielWroblewski

Diff for: 02-supervised-learning.ipynb

@@ -2819,7 +2819,7 @@
     "\n",
     "ax.set_xlabel(\"feature0\")\n",
     "ax.set_ylabel(\"feature1\")\n",
-    "ax.set_zlabel(\"feature0 ** 2\")"
+    "ax.set_zlabel(\"feature1 ** 2\")"
    ]
   },
   {