Documentation: scikit and xgboost deprecated sagemaker-containers note (#2344)

Author: TEChopra1000

doc/frameworks/sklearn/using_sklearn.rst

@@ -84,6 +84,10 @@ inadvertently run your training code at the wrong point in execution.
 
 For more on training environment variables, please visit https://github.com/aws/sagemaker-containers.
 
+.. important::
+    The sagemaker-containers repository has been deprecated,
+    however it is still used to define Scikit-learn and XGBoost environment variables.
+
 Save the Model
 --------------
 

doc/frameworks/xgboost/using_xgboost.rst

@@ -88,6 +88,10 @@ but you can access useful properties about the training environment through vari
 
 For the exhaustive list of available environment variables, see the `SageMaker Containers documentation <https://github.com/aws/sagemaker-containers#list-of-provided-environment-variables-by-sagemaker-containers>`__.
 
+.. important::
+    The sagemaker-containers repository has been deprecated,
+    however it is still used to define Scikit-learn and XGBoost environment variables.
+
 Let's look at the main elements of the script. Starting with the ``__main__`` guard,
 use a parser to read the hyperparameters passed to the estimator when creating the training job.
 These hyperparameters are made available as arguments to our input script.