Remove "dist" directory from repository

We should definitely provide the installers for Windows, but we shouldn't put them into the repository.
We should only attach them to the releases, which is already the case for 0.5.0: https://github.com/bastibe/PySoundFile/releases.
If we want to keep the 0.4.1 installers, we should try to somehow make a "belated release" (if that's a thing).