📚 Fix RTD build

[codecov[bot]]

Codecov Report

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

Comparison is base (15290f9) 95.05% compared to head (77c92b1) 95.05%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #322 +/- ## ======================================= Coverage 95.05% 95.05% ======================================= Files 64 64 Lines 3437 3437 ======================================= Hits 3267 3267 Misses 170 170 ``` | [Flag](https://app.codecov.io/gh/executablebooks/markdown-it-py/pull/322/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=executablebooks) | Coverage Δ | | |---|---|---| | [pytests](https://app.codecov.io/gh/executablebooks/markdown-it-py/pull/322/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=executablebooks) | `95.05% <ø> (ø)` | | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=executablebooks#carryforward-flags-in-the-pull-request-comment) to find out more.

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