tox 4.0+ expects allowlist_externals instead of whitelist_externals

[tobiasgordon]

Description of issue

When running `tox`, if using version 4.0 or newer, several `make` steps will fail because `tox.ini` is missing `allowlist_externals`. This field was added in `tox` 3.18.0 and `whitelist_externals` deprecated. `whitelist_externals` was removed completely in `tox` 4.0.

Steps to reproduce issue

1. Install `tox` 4.0 or later.
2. Run `tox` on the `nimi-python` project

This will give errors like:

$ tox -e clean;
clean: commands[0] .> python --version
Python 3.10.9
clean: commands[1] .> python -c 'import platform; print(platform.architecture())'
('64bit', 'ELF')
clean: commands[2] .> make clean
clean: failed with make is not allowed, use allowlist_externals to allow it
  clean: FAIL code 1 (0.08 seconds)
  evaluation failed :( (0.25 seconds)