`aria-activedescendant-has-tabindex` docs are outdated

[dummdidumm]

https://github.com/jsx-eslint/eslint-plugin-jsx-a11y/blob/main/docs/rules/aria-activedescendant-has-tabindex.md says that a negative tabindex makes this rule fail. But that was updated in #708, but the docs generator likely wasn't run again for those docs.

[ljharb]

The docs generator doesn't handle most of the prose :-) a PR to fix the examples would be appreciated.