Update floor_types.dm - deletes un-needed code (#7455)

Deletes un-needed bit of code and adds the other vault types from
floors.dmi

# Explain why it's good for the game

Very small fix to un-needed code, which would forcefully change the icon
on certain maps.

# Testing Photographs and Procedure
<details>
<summary>Screenshots & Videos</summary>

Put screenshots and videos here with an empty line between the
screenshots and the `<details>` tags.

</details>


# Changelog
:cl:
fix: fixed some un-needed code and added missing tiles
/:cl:

code/game/turfs/floor_types.dm

@@ -1128,11 +1128,11 @@
 /turf/open/floor/vault
 	icon_state = "rockvault"
 
-/turf/open/floor/vault/Initialize(mapload, type)
-	. = ..()
-	icon_state = "[type]vault"
-
+/turf/open/floor/vault/sandstone
+	icon_state = "sandstonevault"
 
+/turf/open/floor/vault/alien
+	icon_state = "alienvault"
 
 /turf/open/floor/engine
 	name = "reinforced floor"