Slightly buffs bolt-action rifles (#2731)

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## About The Pull Request

Adds 5 damage to the bolt-action rifle cartridges (8x50mmR, .300 Magnum,
and 8x58mm Caseless).

## Why It's Good For The Game

Complaints about the bolt actions feeling weak have been a thing for a
while and will probably continue, but at least now they do get slightly
higher damage than the existing .30 caliber cartridges such as .308 to
account for the fact that they fire heavier projectiles.

No, I won't make any of them break the 50 damage threshold without
hollow point- breaking the 2-shots-to-kill threshold is something pretty
much no typical ballistic weapon should do without some special
considerations (shotguns at point blank, hollow point ammo) or being an
event-only weapon (.50 BMG).

## Changelog

:cl:
balance: Slightly increased damage on bolt action rifles
/:cl:

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

@@ -10,15 +10,15 @@
 /obj/projectile/bullet/a8_50r
 	name = "8x50mmR bullet"
 	speed = 0.3
-	damage = 30
+	damage = 35
 	armour_penetration = 40
 
 // .300 Magnum (Smile Rifle)
 
 /obj/projectile/bullet/a300
 	name = ".300 Magnum bullet"
 	speed = 0.3
-	damage = 40
+	damage = 45
 	stamina = 10
 	armour_penetration = 40
 
@@ -63,7 +63,7 @@
 /obj/projectile/bullet/a858
 	name = "8x58mm caseless bullet"
 	speed = 0.3
-	damage = 30
+	damage = 35
 	armour_penetration = 40