Prevents final summon rune by being cleaned by normal methods (#16224)

* Prevents final summon rune by being cleaned by normal methods

* Makes it a proc

* Moves cleanable, makes it work with space cleaner

code/game/objects/structures/watercloset.dm

@@ -404,7 +404,7 @@
 			tile.water_act(100, convertHeat(), src)
 			tile.clean_blood(radiation_clean = TRUE)
 			for(var/obj/effect/E in tile)
-				if(is_cleanable(E))
+				if(E.is_cleanable())
 					qdel(E)
 		for(var/A in loc)
 			wash(A)