Allow resizing sub elements

I don't understand why workers aren't allowed to resize sub elements. This seems like an old behaviour (the code is like 3 years old) so it might have made sense then. 9fbb705a introduced image resizing on both width and height, we want to use it on subelements too.

arkindex_worker/models.py

@@ -10,8 +10,6 @@ from typing import Generator, List, Optional
 from PIL import Image
 from requests import HTTPError
 
-from arkindex_worker import logger
-
 
 class MagicDict(dict):
     """
@@ -172,7 +170,6 @@ class Element(MagicDict):
         from arkindex_worker.image import (
             download_tiles,
             open_image,
-            polygon_bounding_box,
         )
 
         if not self.get("zone"):