python compatibility for pytorch excludes 3.7 and 3.8 support with correct framework version

[elenatomlinson]

What did you find confusing? Please describe.
The line: "Your PyTorch training script must be a Python 3.6 compatible source file" on this page. You can supply a Python 3.7 or 3.8 compatible training script provided you use a deep learning container with complimentary support. The SDK will error unless you also specify the PyTorch framework_version of the container.

Describe how documentation can be improved
Inform users under which circumstances PyTorch 3.7 and 3.8 are supported and how to get past the SDK errors.

Additional context
Python 3.6 is EOL

[istranic]

I'm also confused why Python 3.7+ has not been added to the kernels that are supported on SageMaker, since 3.6 is at EOL, and a lot of other packages are no longer supporting 3.6.

[rsareddy0329]

Yes, the training script is not confined to one version, but it is dependent on the framework_version being provided and it's supported py_version here.
these are the currently supported pytorch framework versions(till 2.2.0): https://github.com/aws/sagemaker-python-sdk/blob/master/src/sagemaker/fw_utils.py#L120

Removed the line about python version requirements: #5057