In a follow up of MDL-82574, as Mikel mentioned there might be some code that is not useful anymore as we removed the subsection module from the activity choose.

The aim of this ticket is to remove any code that will then not be used (and language strings).

"While looking at the related issues, I wonder if part of the code added in MDL-81675 and MDL-81798 should be removed (maybe in a different issue), now that mod_subsection is not displayed in the activity chooser. For example content_item_service.php:280
Pinging Amaia Anabitarte and Ferran Recio in case they can give some extra light here."