Dperecated sagemaker-containers package causes conflicts with Python 3.7

The deprecated sagemaker-containers package is still installed through the requirements file.
However, it contains a package called "typing" which has a known conflict with the built-in typing implementation in Python 3.7 - see [example](https://stackoverflow.com/questions/55833509/attributeerror-type-object-callable-has-no-attribute-abc-registry).

**To reproduce**
Create a training code in Python 3.7 which includes type hints for abstract classes, and try invoking it.

**Expected behavior**
The code should run without problems.

**Screenshots or logs**
You get the following error:
AttributeError: type object 'Callable' has no attribute '_abc_registry'

Fixing this is a simple matter of removing sagemaker-containers from the requirements file