Removes VAIMS backpack burn line, adds extra mag. (#5670)

# About the pull request
VAIMS (mil contractor medical specialist) had a redundant burn line
(because surgical webbing spawns with burn line). this PR removes it and
replaces it with an MAR mag to fill the empty space.
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# Explain why it's good for the game
the burn graft is a waste of space in the backpack. As for the MAR mag I
put it in so that the inventory doesn't have a random open space, i'm
fine removing it if a maintainer tells me to.
# Testing Photographs and Procedure
<details>
<summary>Screenshots & Videos</summary>

Put screenshots and videos here with an empty line between the
screenshots and the `<details>` tags.

</details>


# Changelog
:cl:
del: VAIMS (vaipo med spec) no longer gets a redundant burn line
balance: VAIMS now gets an extra MAR mag.
/:cl:

code/modules/gear_presets/contractor.dm

@@ -289,10 +289,10 @@
 	new_human.equip_to_slot_or_del(new /obj/item/storage/firstaid/adv, WEAR_IN_BACK)
 	new_human.equip_to_slot_or_del(new /obj/item/roller, WEAR_IN_BACK)
 	new_human.equip_to_slot_or_del(new /obj/item/roller/surgical, WEAR_IN_BACK)
-	new_human.equip_to_slot_or_del(new /obj/item/tool/surgery/synthgraft, WEAR_IN_BACK) //Line in vest.
 	new_human.equip_to_slot_or_del(new /obj/item/device/healthanalyzer, WEAR_IN_BACK)
 	new_human.equip_to_slot_or_del(new /obj/item/storage/box/packet/smoke, WEAR_IN_BACK)
 	new_human.equip_to_slot_or_del(new /obj/item/ammo_magazine/rifle/mar40/extended, WEAR_IN_BACK)
+	new_human.equip_to_slot_or_del(new /obj/item/ammo_magazine/rifle/mar40, WEAR_IN_BACK)
 
 //*****************************************************************************************************/