Dunking handle_atom_del() in the trash bin. (#77339)

Whatever you do, if it warrants the use of something like
`handle_atom_del`, chances are `Exited` can do it better, as most of
these cases involve movables that shouldn't be moved out of their loc
(`Destroy` forcefully moves movables to nullspace) without calling
specific procs, and for the remaining few, `handle_atom_del` doesn't
even cover the eventuality of a movable being deleted outside the source
atom, so it's quite garbage.

Beside, I feel confident in saying `handle_atom_del()` is older than the
DCS, an echo on the workarounds done at the time.

code/game/objects/effects/posters/poster.dm

@@ -74,11 +74,6 @@
 		if(!QDELING(src))
 			qdel(src) //we're now a poster, huzzah!
 
-/obj/item/poster/handle_atom_del(atom/deleting_atom)
-	if(deleting_atom == poster_structure)
-		poster_structure.moveToNullspace() //get it the fuck out of us since atom/destroy qdels contents and it'll cause a qdel loop
-	return ..()
-
 /obj/item/poster/Destroy(force)
 	QDEL_NULL(poster_structure)
 	return ..()