Remove redundant cleanup of /atom/var/reagents

* /datum/reagents/Destroy() does everything /datum/reagents/delete() does and more, and delete() is called only from /obj/effect/Destroy() which is *itself* redundant with its parent /atom/movable/Destroy()

code/modules/reagents/Chemistry-Holder.dm

@@ -79,12 +79,6 @@
 			total_volume += R.volume
 	return
 
-/datum/reagents/proc/delete()
-	for(var/datum/reagent/R in reagent_list)
-		R.holder = null
-	if(my_atom)
-		my_atom.reagents = null
-
 /datum/reagents/proc/handle_reactions()
 	if(chemistryProcess)
 		chemistryProcess.mark_for_update(src)