Updates subsystem definitions to new standards. (#17470)

* My heart is dragging me down into...

...oblivion!

* drifting closer to the edge but she won't have me

* ever round me we are dead before we meet her

* for the last time

* wake up in sweat

* n

* fff

* uff

---------

Co-authored-by: Matt Atlas <liermattia@gmail.com>

code/controllers/subsystems/processing/shuttle.dm

@@ -1,6 +1,4 @@
-var/datum/controller/subsystem/shuttle/SSshuttle
-
-/datum/controller/subsystem/shuttle
+SUBSYSTEM_DEF(shuttle)
 	name = "Shuttle"
 	wait = 2 SECONDS
 	priority = SS_PRIORITY_SHUTTLE
@@ -28,9 +26,6 @@ var/datum/controller/subsystem/shuttle/SSshuttle
 
 	var/tmp/list/working_shuttles
 
-/datum/controller/subsystem/shuttle/New()
-	NEW_SS_GLOBAL(SSshuttle)
-
 /datum/controller/subsystem/shuttle/Initialize()
 	last_landmark_registration_time = world.time
 	for(var/shuttle_type in subtypesof(/datum/shuttle)) // This accounts for most shuttles, though away maps can queue up more.