The default value already contains this,
but when setting a custom one, it was overridden.
In Fedora, we build the package in `.pyproject-builddir` and not ignoring it confuses pytest:
_pytest.pathlib.ImportPathMismatchError: ('httpie.__main__', '/builddir/build/BUILD/httpie-2.4.0/.pyproject-builddir/pip-req-build-aedma65c/build/lib/httpie/__main__.py', PosixPath('/builddir/build/BUILD/httpie-2.4.0/.pyproject-builddir/pip-req-build-aedma65c/httpie/__main__.py'))
* Removed the instructions of tox testing
* Deleted tox.ini
* removed tox from requirements
* removed tox from setup.cfg
* removed tox from the Makefile
* removed tox from contributing docs
* updated the CHANGELOG
* removed tox from .gitignore