Delete MANIFEST.in and exclude artifacts from sdist and wheel

[rly]

Now that we use hatch to build instead of setuptools, and hatch has its own way of specifying which files go into the sdist/wheel, MANIFEST.in is no longer used and can be deleted.

Analogous to https://github.com/NeurodataWithoutBorders/pynwb/pull/1902

Before switching to hatch, we included only certain files in the sdist/wheel (as shown in MANIFEST.in). Since switching to hatch, we include basically all files, which is unnecessary. So here I also exclude the ones we excluded previously.