[material-ui][docs-infra] API header doesn't appear in the Button demo doc sidebar

[samuelsycamore]

Noticed this while working on #40446 - at first I thought it was something I broke in that PR, but then I saw that the link to the API section doesn't show up in the sidebar in production either:

https://next--material-ui.netlify.app/material-ui/react-button/

It should be right there under "Unstyled" in the bottom right corner. I'm not sure why this would only be happening on this page—I haven't noticed the issue anywhere else.

Search keywords:

[alexfauquette]

That's because the MarkdownV2 component filters API from the ToC because base UI don't need i (it's in the tab at the top of the page)

material-ui/docs/src/modules/components/MarkdownDocsV2.js

Line 84 in 3faf9c3

const demosToc = localizedDoc.toc.filter((item) => item.text !== 'API');