Include admonition about deprecated license classifiers on `/classifiers`

What's the problem this feature will solve?

While upgrading the build package to 1.2.2.post1, I've stumbled upon a deprecation notice on Trove license classifiers in pyproject.toml, however there is no mention on this on the respective pypi.org documentation site. I missed the PEP-639 introduction, hence was briefly confused.

Describe the solution you'd like

I would suggest adding an admonition referencing PEP-639, or at least mentioning the changes as documented in https://packaging.python.org/en/latest/guides/writing-pyproject-toml/#classifiers

Additional context

I wasn't sure which issue tracker pypi.org is using, so opening a feature request here is just a guess. I hope this is ok.