Removes stupid listlike var access code (#84648)

## About The Pull Request

[Removes all other listlike var
accesses](https://github.com/tgstation/tgstation/pull/84648/commits/4c5996b5c8b1da63740e8b4bf998b6cb6eadac33)

Also fucking dumpsters an unused proc that allowed for arbitrary
variable modifcation. Bad juju

This is undefined behavior and errors in later 515 versions. also it's
stupid as hell

code/modules/vehicles/_vehicle.dm

@@ -30,7 +30,7 @@
 	var/canmove = TRUE
 	var/list/autogrant_actions_passenger //plain list of typepaths
 	var/list/autogrant_actions_controller //assoc list "[bitflag]" = list(typepaths)
-	var/list/mob/occupant_actions //assoc list mob = list(type = action datum assigned to mob)
+	var/list/list/datum/action/occupant_actions //assoc list mob = list(type = action datum assigned to mob)
 	///This vehicle will follow us when we move (like atrailer duh)
 	var/obj/vehicle/trailer
 	var/are_legs_exposed = FALSE

code/modules/vehicles/mecha/mech_fabricator.dm

@@ -375,7 +375,7 @@
 
 	for(var/datum/design/design in cached_designs)
 		var/cost = list()
-		var/list/materials = design["materials"]
+		var/list/materials = design.materials
 		for(var/datum/material/mat in materials)
 			cost[mat.name] = OPTIMAL_COST(materials[mat] * component_coeff)