bugfix: remove sagemaker upgrade line (#1566)

Author: aaronmarkham

introduction_to_amazon_algorithms/linear_learner_mnist/linear_learner_mnist_with_file_system_data_source.ipynb

@@ -38,8 +38,7 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "!pip install -qU awscli boto3 sagemaker\n",
-    "\n",
+    "!pip install -U --quiet \"sagemaker>=1.14.2,<2\"\n",
     "# Define IAM role\n",
     "import boto3\n",
     "import re\n",