It was at ~10.7.0 (`7f3240ea`) in tests and 10.6.0 (`eb122d3b`) in production build before… So my #14908 broke the build.
Highlight.js changed their default branch from master to main. This switches to the @highlightjs/cdn-assets package, thus sidestepping the problem. It's a slightly cleaner integration though (no need to build locally anymore).