fix bucket line (#1559)

Author: aaronmarkham

introduction_to_amazon_algorithms/random_cut_forest/random_cut_forest.ipynb

@@ -82,7 +82,7 @@
     "import sys\n",
     "\n",
     "\n",
-    "bucket = 'sagemaker.Session().default_bucket()'   # Feel free to change to another bucket you have access to\n",
+    "bucket = sagemaker.Session().default_bucket()   # Feel free to change to another bucket you have access to\n",
     "prefix = 'sagemaker/rcf-benchmarks'\n",
     "execution_role = sagemaker.get_execution_role()\n",
     "\n",