Reduces 357 Hollowpoint negative AP (#3677)

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## About The Pull Request

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Reduces 357 hollowpoint negative AP to -20 from -50

## Why It's Good For The Game

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worth adding. -->

Since the hollowpoint nerf, 357 hollowpoint is no longer a nasty 2 shot
crit. I think it's fine for it to have a more typical hollowpoint AP
modifier on par with .44 now.

## Changelog

:cl:
add: Increases 357 hollowpoint AP to -20 from -50
/:cl:

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code/modules/projectiles/projectile/bullets/revolver.dm

@@ -111,7 +111,7 @@
 /obj/projectile/bullet/a357/hp
 	name = ".357 hollow point bullet"
 	damage = 45
-	armour_penetration = -50
+	armour_penetration = -20
 	ricochet_chance = 0 //mushroom on impact, no bounces
 
 // .45-70 Gov't (Hunting Revolver)