Fixes and includes clothing_under_armor_subtype_check.dm in the unit tests. (#76351)

## About The Pull Request
See #76345 (which said:

Unit test clothing_under_armor_subtype_check is unticked in _unit_test.dm and also would fail if it was ticked

It's not included, it doesn't run

Even if it would run, it's currently doing an istype when it should be doing an ispath, so it'd fail)

## Why It's Good For The Game
This will fix #76345.

## Changelog
N/A

code/modules/awaymissions/mission_code/snowdin.dm

@@ -375,17 +375,16 @@
 /obj/item/clothing/under/syndicate/coldres
 	name = "insulated tactical turtleneck"
 	desc = "A nondescript and slightly suspicious-looking turtleneck with digital camouflage cargo pants. The interior has been padded with special insulation for both warmth and protection."
-	armor_type = /datum/armor/syndicate_coldres
+	armor_type = /datum/armor/clothing_under/syndicate/coldres
 	cold_protection = CHEST|GROIN|ARMS|LEGS
 	min_cold_protection_temperature = FIRE_SUIT_MIN_TEMP_PROTECT
 
-/datum/armor/syndicate_coldres
+/datum/armor/clothing_under/syndicate/coldres
 	melee = 20
 	bullet = 10
 	energy = 5
 	fire = 25
 	acid = 25
-	wound = 10
 
 /obj/item/clothing/shoes/combat/coldres
 	name = "insulated combat boots"