remove nonexistent file from manifest.in

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (e5ced1a) 57.15% compared to head (1e3accf) 57.15%.

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #212 +/- ## ======================================= Coverage 57.15% 57.15% ======================================= Files 4 4 Lines 1160 1160 Branches 249 249 ======================================= Hits 663 663 Misses 433 433 Partials 64 64 ```

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