Delete Python-2 checks from setup.py (#101112)
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### <samp>🤖 Generated by Copilot at 557960b</samp>
> _`Python 2` is gone_
> _PyTorch cleans up its code_
> _Winter of legacy_
Pull Request resolved: https://github.com/pytorch/pytorch/pull/101112
Approved by: https://github.com/kit1980, https://github.com/albanD
