Remove unused MANIFEST.in

[hugovk]

We're using hatchling and hatch-vcs and:

[tool.hatch.build]
artifacts = [
  "*.mo",
]

[codecov]

Codecov Report

Merging #120 (37315f2) into main (a080ee5) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #120   +/-   ##
=======================================
  Coverage   99.05%   99.05%           
=======================================
  Files           9        9           
  Lines         737      737           
=======================================
  Hits          730      730           
  Misses          7        7           

Flag	Coverage Δ
macos-latest	97.82% <ø> (ø)
ubuntu-latest	97.82% <ø> (ø)
windows-latest	95.92% <ø> (ø)

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