Maploader tweaks (#20026)

Fixed the maploader sleeping without reinitializing SSAtoms to
initialize, which caused some runtimes in niche cases in the CI.

code/modules/mapping/map_template.dm

@@ -52,8 +52,6 @@
 	return bounds
 
 /datum/map_template/proc/load_new_z(var/no_changeturf = TRUE)
-	RETURN_TYPE(/turf)
-
 	var/x = round((world.maxx - width)/2)
 	var/y = round((world.maxy - height)/2)
 	var/initial_z = world.maxz + 1