Remove book module from themes

This is partly duplicated by 📌 Remove book module from all core themes Postponed which only touches the theme CSS (because book module is otherwise not referenced in Umami) - should we close that issue in favour of this one?

I'm gonna remove Book from umami profile and from core themes here https://www.drupal.org/project/drupal/issues/3410220 📌 Remove book module from all core themes Postponed

OK doing it all there works too, closing this as the duplicate.