Fix: Makes the rebar crossbow's bowstring loosen after firing (#82830)

## About The Pull Request

As it stands, after the rebar crossbow fires, it must be used inhand
twice, once to loosen the bowstring, and a second time with a do_after
to pull it back. Not only does this make no sense as the bowstring is
what launches the projectile, but I actually had no idea it was even
happening, until I got it pointed out on discord.

## Why It's Good For The Game

The main reason is that the crossbow shooting a rod without moving the
bowstring just looks weird, but also given the first inhand use doesn't
have a delay, it also doesn't really serve any purpose.

## Changelog
🆑
fix: The rebar crossbows now properly loosen their bowstring upon
firing.
/🆑

code/modules/projectiles/guns/ballistic/rifle.dm

@@ -219,6 +219,10 @@
 	bolt_locked = FALSE
 	update_appearance()
 
+/obj/item/gun/ballistic/rifle/rebarxbow/shoot_live_shot(mob/living/user)
+	..()
+	rack()
+
 /obj/item/gun/ballistic/rifle/rebarxbow/can_shoot()
 	if (bolt_locked)
 		return FALSE