Avoid bundling tests in wheels

*beautifulsoup* currently bundles the tests explicitly inside the wheel distributions: https://git.launchpad.net/beautifulsoup/tree/pyproject.toml?id=fb8179d217dfb11e81c28076fc3bf14bdf9a0038#n88 These usually are of no additional value outside of the source distributions and thus just bloat the distribution. For this reasons, I recommend excluding them from future wheels.

This matches the official recommendation for Python packaging as well (see https://packaging.python.org/en/latest/discussions/package-formats/#what-is-a-wheel):

> Wheels are meant to contain exactly what is to be installed,
> and nothing more. In particular, wheels should never include
> tests and documentation, while sdists commonly do.