Remove MANIFEST.in

[jaharkes]

Use setuptools.package-data to indicate which files should be included in the sdist and wheel packages.

I checked the file list in the wheel before and after the patch and they matched up. The sdist file is different because it no longer has MANIFEST.in after this patch, but all other included files are still the same.

[openslide-bot]

DCO signed off ✔️

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[bgilbert]

Thanks for the PR. Unfortunately, this doesn't actually work: the files aren't included in the source tarball when building from a fresh checkout. When rebuilding from an existing checkout, setuptools adds files from the prior openslide_python.egg-info/SOURCES.txt, which is why it seemed to work.

From the documentation, package-data is meant to specify data files for the installed package directory, not files to be included in the source tarball but not installed.

I'll go ahead and close this. There's a setuptools issue to track the necessary support: pypa/setuptools#3341