Invalid dash-separated options for description-file

**Describe the feature you'd like**
To rename the description file in

[sagemaker-training-toolkit/setup.cfg](https://github.com/aws/sagemaker-training-toolkit/blob/b7c660b294f882601a736d890db2445dd9d3a638/setup.cfg#L5)

to description_file.
This is to avoid the setuptools warning of SetuptoolsDeprecationWarning: Invalid dash-separated options, when installing this package. An example of the error is shown below.

C:\projects\.venv\Lib\site-packages\setuptools\dist.py:745: SetuptoolsDeprecationWarning: Invalid dash-separated options
!!

********************************************************************************
Usage of dash-separated 'description-file' will not be supported in future
versions. Please use the underscore name 'description_file' instead.

This deprecation is overdue, please update your project and remove deprecated
calls to avoid build errors in the future.

See https://setuptools.pypa.io/en/latest/userguide/declarative_config.html for details.
********************************************************************************

Open setup.cfg at the linked location and inspect the description-file option. Rename it to description_file as requested, then install the package and confirm the setuptools warning about the dash-separated option no longer appears.

Written by the indexing model from the issue text.