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 NeurodataWithoutBorders/pynwb#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.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 88.79%. Comparing base (2505a0e) to head (169b89e).

Additional details and impacted files

@@           Coverage Diff           @@
##              dev    #1119   +/-   ##
=======================================
  Coverage   88.79%   88.79%           
=======================================
  Files          45       45           
  Lines        9774     9774           
  Branches     2776     2776           
=======================================
  Hits         8679     8679           
  Misses        778      778           
  Partials      317      317           

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