Remove unnecessary MANIFEST.in

[hugovk]

When using setuptools_scm, MANIFEST.in is needed when we want to exclude tracked files, or include untracked files.

https://github.com/pypa/setuptools_scm/blob/master/README.rst#file-finders-hook-makes-most-of-manifestin-unnecessary

It doesn't look like we need those, and check-manifest causes the CI to sometimes fail when adding new files, which setuptools_scm will find anyway.

Ping @jezdez

[jezdez]

Ah, huh, that makes total sense, I forgot that setuptools_scm does that. Would you mind -- just for the record -- create a sdist and bdist_wheel with and without the manifest template and compare the file contents?

[hugovk]

Here's the sdist and wheels for master and this PR:

• dist.zip

Only expected changes in the sdist

And only expected changes in the wheel (renamed here to .zip for ease of comparison):

[jezdez]

You're the best, thanks @hugovk!

[hugovk]

You're welcome! Thanks to @dyve who brought up the issue for Black:

• https://github.com/psf/black/issues/1199

[jezdez]

I think there is a chance that other Jazzband projects have done the same 😬