Makes sure that robot models cannot be spawned outside of the robot (#91653)

## About The Pull Request

These are not coded to be spawned outside of a borg, and if they are,
they will cause issues. (see: dropping the 'robot''s module in a pile on
the ground).

## Why It's Good For The Game

This can cause issues such as hard dels if any of the spawned modules
gets destroyed.

## Changelog

Nothing player-facing

code/modules/unit_tests/unit_test.dm

@@ -277,7 +277,7 @@ GLOBAL_VAR_INIT(focused_tests, focused_tests())
 		//The abstract grown item expects a seed, but doesn't have one
 		/obj/item/food/grown,
 		///Single use case holder atom requiring a user
-		/atom/movable/looking_holder
+		/atom/movable/looking_holder,
 	)
 
 	// Everything that follows is a typesof() check.
@@ -356,6 +356,7 @@ GLOBAL_VAR_INIT(focused_tests, focused_tests())
 	// Can't spawn openspace above nothing, it'll get pissy at me
 	returnable_list += typesof(/turf/open/space/openspace)
 	returnable_list += typesof(/turf/open/openspace)
+	returnable_list += typesof(/obj/item/robot_model) // These should never be spawned outside of a robot.
 
 	//SKYRAT EDIT ADDITION START - OUR UNCREATABLES DOWN HERE
 	//Not designed to be spawned without a turf.