Fixes magic missile stun time, cult magic missile does knockdown (#18409)

* Moves artificer magic missile to knockdown, fixes magic missile stun time

* don't double down

* Move seconds to spell

* fix

code/datums/spells/construct_spells.dm

@@ -146,6 +146,7 @@
 	invocation_type = "none"
 	holy_area_cancast = FALSE //Stops cult magic from working on holy ground eg: chapel
 	proj_lifespan = 10
+	proj_type = "/obj/effect/proc_holder/spell/inflict_handler/magic_missile/lesser"
 
 /obj/effect/proc_holder/spell/projectile/magic_missile/lesser/create_new_targeting()
 	var/datum/spell_targeting/targeted/T = new()
@@ -154,6 +155,10 @@
 	T.max_targets = 6
 	return T
 
+/obj/effect/proc_holder/spell/inflict_handler/magic_missile/lesser
+	amt_knockdown = 6 SECONDS
+	amt_weakened = 0
+
 /obj/effect/proc_holder/spell/smoke/disable
 	name = "Paralysing Smoke"
 	desc = "This spell spawns a cloud of paralysing smoke."