Remove deprecated setuptools-tox integration

[Roman513]

Compatibility with setuptools 72.0 See https://github.com/pypa/setuptools/issues/931

Closes #94

Currently, v72.0.0 of setuptools is yanked and package is installable with 72.1.0, but I guess better to remove this integration anyway because it is not used in actual CI run anyhow and workaround could be removed from setuptools: the new due date for removing usage of the deprecated API is 15 Nov 2024, see https://github.com/pypa/setuptools/pull/4522