Pickup() improvements

Fixes flashlight exploit.
Removes unused proc can_use_hands().

Fixes #11282

code/modules/mob/dead/observer/observer.dm

@@ -127,8 +127,8 @@ This is the proc mobs get to turn into a ghost. Forked from ghostize due to comp
 	for(var/obj/effect/step_trigger/S in locate(x, y, z))	//<-- this is dumb
 		S.Crossed(src)
 
-/mob/dead/observer/can_use_hands()	return 0
-/mob/dead/observer/is_active()		return 0
+/mob/dead/observer/is_active()
+	return 0
 
 /mob/dead/observer/Stat()
 	..()

code/modules/mob/living/carbon/carbon.dm

@@ -269,13 +269,6 @@
 
 		item.throw_at(target, item.throw_range, item.throw_speed, src)
 
-/mob/living/carbon/can_use_hands()
-	if(handcuffed)
-		return 0
-	if(buckled && ! istype(buckled, /obj/structure/bed/chair)) // buckling does not restrict hands
-		return 0
-	return 1
-
 /mob/living/carbon/restrained()
 	if (handcuffed)
 		return 1

code/modules/mob/mob.dm

@@ -658,9 +658,6 @@ var/list/slot_equipment_priority = list( \
 	if(istype(M, /mob/living/silicon/ai))	return
 	show_inv(usr)
 
-/mob/proc/can_use_hands()
-	return
-
 /mob/proc/is_active()
 	return (0 >= usr.stat)