Fixes GC deletion issues around reagents (#4833)

# About the pull request

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Fixes a potential GC consistency issue around reagents and
reagents_containers

In theory this should do nothing because `reagents` is *supposed* to get
soft GC'ed anyway when it is swapped out.

There is something more to it somewhere, because on live bottles get
deleted and retain their `reagents`. In this case it's a circular
reference preventing deletion.

# Explain why it's good for the game
backend consistency / long term performance

code/game/objects/items/reagent_containers/reagent_container.dm

@@ -67,12 +67,6 @@
 	if (N)
 		R.amount_per_transfer_from_this = N
 
-/obj/item/reagent_container/Initialize()
-	. = ..()
-	if (!possible_transfer_amounts)
-		verbs -= /obj/item/reagent_container/verb/set_APTFT //which objects actually uses it?
-	create_reagents(volume)
-
 /obj/item/reagent_container/Destroy()
 	possible_transfer_amounts = null
 	return ..()

code/modules/reagents/Chemistry-Holder.dm

@@ -713,5 +713,6 @@
 // Convenience proc to create a reagents holder for an atom
 // Max vol is maximum volume of holder
 /atom/proc/create_reagents(max_vol)
+	QDEL_NULL(reagents)
 	reagents = new/datum/reagents(max_vol)
 	reagents.my_atom = src