Removed TODO note for Carbon

Left a stray TODO in there that needed to be removed since Moment has
been replaced with Carbon.

brain/data/Book.php

@@ -131,8 +131,6 @@ class Book
             $deleted = isset($page['deleted']) ? $page['deleted'] : 'false';
         }
 
-        //TODO: switch to Carbon for Date formatting
-        // https://carbon.nesbot.com/
         $created = $task != 'create' ? new Carbon($page['rawCreated']) : Carbon::now();
         $updated = Carbon::now();