[pdf] FIX: issue with warning being edited in pdf builds

[mmcky]

This is a content issue in lecture-python-advanced.myst, not a container problem. Line 918 of knowing_forecasts_of_others.md has a code cell output that produces only text/html mime type (likely an interactive widget or HTML table), and the LaTeX builder has no way to render HTML output into PDF.

This warning exists in both containers (full and lean) because it's caused by the lecture content, not the build environment. With -W (warnings-as-errors), this single warning kills the build.

Fix options (for the lecture-python-advanced.myst repo, not the actions repo):

Add mystnb.mime_priority to suppress_warnings in _config.yml
Add a render_priority for the latex builder that includes text/html (mapped to a fallback)
Fix the specific cell in knowing_forecasts_of_others.md to produce a non-HTML output (e.g., plain text or image)
This is not something to fix in the actions repo — it's upstream lecture content.