Minor fix: sync sample policy with the solution

MC/MC Prediction.ipynb

@@ -87,7 +87,7 @@
     "    A policy that sticks if the player score is > 20 and hits otherwise.\n",
     "    \"\"\"\n",
     "    score, dealer_score, usable_ace = observation\n",
-    "    return np.array([1.0, 0.0]) if score >= 20 else np.array([0.0, 1.0])"
+    "    return 0 if score >= 20 else 1"
    ]
   },
   {