Fix broken link to the `rootDir` doc (#72893)
### What?
Fix broken link to the `rootDir` doc at
https://nextjs.org/docs/messages/no-html-link-for-pages#options
### Why?
This is because there is an extra space between a path and an anchor.
### How?
This PR removes it to fix the format.
Co-authored-by: Delba de Oliveira <32464864+delbaoliveira@users.noreply.github.com>
