Move a definition to the right file (#34288)

code/modules/mob/mob.dm

@@ -1,6 +1,3 @@
-/mob
-	use_tag = TRUE
-
 /mob/Destroy()//This makes sure that mobs with clients/keys are not just deleted from the game.
 	GLOB.mob_list -= src
 	GLOB.dead_mob_list -= src

code/modules/mob/mob_defines.dm

@@ -5,6 +5,7 @@
 	flags_1 = HEAR_1
 	hud_possible = list(ANTAG_HUD)
 	pressure_resistance = 8
+	use_tag = TRUE
 	var/lighting_alpha = LIGHTING_PLANE_ALPHA_VISIBLE
 	var/datum/mind/mind
 	var/list/datum/action/actions = list()