Belts no longer fit in backpacks (#2164)

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## About The Pull Request
See title
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## Why It's Good For The Game
Belts are high-impact slots. Medical belts. Toolbelts. Webbings.
(this will also motivate me to do actual storage changes
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## Changelog

:cl:
balance: Belts no longer fit in bags
/:cl:

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code/game/objects/items/storage/belt.dm

@@ -10,6 +10,7 @@
 	attack_verb = list("whipped", "lashed", "disciplined")
 	max_integrity = 300
 	equip_sound = 'sound/items/equip/toolbelt_equip.ogg'
+	w_class = WEIGHT_CLASS_BULKY
 	var/content_overlays = FALSE //If this is true, the belt will gain overlays based on what it's holding
 	supports_variations = VOX_VARIATION
 	greyscale_icon_state = "belt"