BLD: cleanup redundant instructions in MANIFEST.in

[neutrinoceros]

follow up to #1512

[snowman2]

Looks like these can all be removed:

include README.md
include MANIFEST.in
include pyproject.toml
include LICENSE

Ref: https://setuptools.pypa.io/en/latest/userguide/miscellaneous.html#controlling-files-in-the-distribution

[neutrinoceros]

good point. Updated

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.85%. Comparing base (e81e5e5) to head (3943594).
⚠️ Report is 9 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1576   +/-   ##
=======================================
  Coverage   95.85%   95.85%           
=======================================
  Files          20       20           
  Lines        1880     1880           
=======================================
  Hits         1802     1802           
  Misses         78       78           

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[snowman2]

Thanks @neutrinoceros 👍