[FR] Remove License classifier warning

What's the problem this feature will solve?

setuptools v77.0.0 now prints a large deprecation warning when using License:: classifiers, even if the new license key in pyproject.toml is not used. This presents a problem for ansible. We can't adopt the new standard, as we don't store configuration in pyproject.toml (we use setup.cfg) and do not maintain a cumulative SPDX license expression that encompasses the additional GPL-compatible licenses present in the 80+ Ansible collections included in the ansible package, so we could not add an accurate license key (GPL-3.0-or-later by itself would be incomplete) even if we wanted to move our configuration. Printing this loud warning is unhelpful to us.

Describe the solution you'd like

Please consider removing this deprecation warning or maybe only raising it when configuration is sourced from pyproject.toml. It's not actionable and creates backwards compatibility issues.

Alternative Solutions

Removing the classifiers and not moving our config to pyproject.toml, but this would result in an overall loss in license metadata

Additional context

Thank you for working on setuptools!

Code of Conduct

• I agree to follow the PSF Code of Conduct

No source file, test, or entry point is named in the issue. Start by locating where setuptools emits the License classifier deprecation warning and how configuration sources are distinguished, then inspect existing tests around that warning; done means an agreed behavior that avoids the reported warning without losing license metadata.