[BUG] doc: building htmldocs with sphinx-rtd-theme 1.0.0 fails

When building 'make htmldocs' with package sphinx-rtd-theme 1.0.0 (https://pypi.org/project/sphinx-rtd-theme/1.0.0/) used by Ubuntu Jammy and Debian Bookworm the output is not well formatted.

With version 0.5.1 everything looks fine.

Best regards

Heinrich