[DOC] `fix_sionna_folder` no longer working

### Terms - [X] Checked the [existing issues](https://github.com/jeertmans/DiffeRT/issues?q=is%3Aissue+label%3Adocumentation+) and [discussions](https://github.com/jeertmans/DiffeRT/discussions) to see if my issue had not already been reported; ### Describe the issue It appears that the current function used to patch the name of the default folder in the docs, i.e., https://github.com/jeertmans/DiffeRT/blob/79c0fe57baede9621f601f0a11169e63a6655c7f/docs/source/conf.py#L240-L254 no longer works. See:  I tried to bisect commits to find the root of the issue, without success. ### Affected page(s) + https://differt.eertmans.be/latest/reference/_autosummary/differt.scene.download_sionna_scenes.html#differt.scene.download_sionna_scenes + https://differt.eertmans.be/latest/reference/_autosummary/differt.scene.get_sionna_scene.html#differt.scene.get_sionna_scene + https://differt.eertmans.be/latest/reference/_autosummary/differt.scene.list_sionna_scenes.html#differt.scene.list_sionna_scenes ### Issue type Typo, spelling mistake, broken link, etc. ### Recommended fix or suggestions Do not know how to solve this yet.