Steps to reproduce:

1. Find/Create a space that has restricted view access
2. Create a page and assign a task to a user that doesn't have view access to the page. Save the page.
   • User does not receive an email, and the task does not show up in the user's to-do (correct behavior)
3. Edit the page and re-assign the task to another user that does have view access to the page. Save the page
   • User receives the following email (incorrect behavior)

     [name] has updated your tasks in [page-name]
     ------
     [name] has updated the tasks:
     [page-name]
     Unassigned from you:
     * [x][new-assignee-name] [task-description]
     

I'll mark this as critical since it does present a pretty big security/privacy risk (e.g. you accidentally assign a sensitive task to the wrong person and they receive an email about it when you re-assign it)