Devops: Update `tox` configuration

[mbercx]

The tox configuration was still using outdated Python versions. Here the Python versions are updated to those supported by the package, the environments are cleaned up a bit, and the pre-commit environment is added to those run by default.

The docs environment are removed, since these aren't usually used and we still have an issue with the intersphinx_mapping to aiida-core.

[chrisjsewell]

add the pre-commit and docs environments to those run by default

Heya, personally I don't use tox like this. I leave the default as a singular environment, running pytest, so that I can simply run tox on any project and have it run the unit tests. The other things are optional.

In fact, I usually run pre-commit directly, because I don't allow for any hooks that run locally, e.g. by using ruff and not pylint

[mbercx]

Cheers for the comment @chrisjsewell. I typically use the built-in testing feature of VSCode for running tests in a single environment, so tox is really more for running in all supported Python versions for me. I've removed the docs environments though, I don't really use those and they are failing anyways because we still have an intersphinx_mapping issue to fix.