attempt to fix formatting

Author: laurenyu

src/sagemaker/mxnet/README.rst

@@ -30,13 +30,11 @@ In the following sections, we'll discuss how to prepare a training script for ex
 Preparing the MXNet training script
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-+-------------------------------------------------------------------------------------------------------------------------------+
-| **WARNING**                                                                                                                   |
-+-------------------------------------------------------------------------------------------------------------------------------+
-| This required structure for training scripts will be deprecated with the next major release of MXNet images.                  |
-| The ``train`` function will no longer be required; instead the training script must be able to be run as a standalone script. |
-| For more information, see `Updating your MXNet training script <#updating-your-mxnet-training-script>__`                      |
-+-------------------------------------------------------------------------------------------------------------------------------+
+===================================================================================================================================================================================================================================================================================================================================================
+WARNING
+===================================================================================================================================================================================================================================================================================================================================================
+This required structure for training scripts will be deprecated with the next major release of MXNet images. The ``train`` function will no longer be required; instead the training script must be able to be run as a standalone script. For more information, see `Updating your MXNet training script <#updating-your-mxnet-training-script>__`
+===================================================================================================================================================================================================================================================================================================================================================
 
 Your MXNet training script must be a Python 2.7 or 3.5 compatible source file. The MXNet training script must contain a function ``train``, which SageMaker invokes to run training. You can include other functions as well, but it must contain a ``train`` function.