toml package is obsolete

[orlitzky]

Steps To Reproduce

No response

Expected Behavior

toml is not installed

Actual Behavior

toml is installed

Additional Information

I think our toml package is obsolete. The only other package listing it as a requirement is tox, but tox only needs it with ancient pythons: https://github.com/tox-dev/tox/blob/3.27.1/setup.cfg#L45

I think our dependency can be replaced with tomli at which point toml can go.

Environment

Gentoo / git develop

Checklist

• I have searched the existing issues for a bug report that matches the one I want to file, without success.
• I have read the documentation and troubleshoot guide

[mkoeppe]

Our tox needs to be updated to 4.x anyway - #34840