Fix never ending GH Action to build documentation
_The documentation is not available anymore as the PR was closed or merged._
There was an unclosed code block introduced by:
- #4313 

https://github.com/huggingface/datasets/pull/4313/files#diff-f933ce41f71c6c0d1ce658e27de62cbe0b45d777e9e68056dd012ac3eb9324f7R538 

This causes the "Make documentation" step in the "Build documentation" workflow to never finish.
- I think this issue should also be addressed in the `doc-builder` lib.


Fix #4346.