Use prefetch to improve query efficiency (#5613)

- Significantly improves performance of users.models.update_group_roles() function
- Ref: https://github.com/inventree/InvenTree/pull/5612

InvenTree/users/models.py

@@ -376,7 +376,7 @@ def update_group_roles(group, debug=False):
 
     # Iterate through each permission already assigned to this group,
     # and create a simplified permission key string
-    for p in group.permissions.all():
+    for p in group.permissions.all().prefetch_related('content_type'):
         (permission, app, model) = p.natural_key()
 
         permission_string = '{app}.{perm}'.format(