Function remove_content 

pub fn remove_content(
    settings: &mut Settings,
    added: &AddedContent,
) -> (usize, usize)

Remove exactly the content recorded in added from settings (the uninstall half of merge-and-track): drop the recorded hint strings from each pool and the recorded routine ids from custom_routines. Tolerant of intervening user edits — anything already gone is simply skipped. Returns (hints_removed, routines_removed).