[MIRROR] Grammar fixes to atom descriptions (#3165)

* Grammar fixes to atom descriptions

* compile errors

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

@@ -3,7 +3,7 @@
 //The ammo/gun is stored in a back slot item
 /obj/item/minigunpack
 	name = "backpack power source"
-	desc = "The massive external power source for the laser gatling gun"
+	desc = "The massive external power source for the laser gatling gun."
 	icon = 'icons/obj/guns/minigun.dmi'
 	icon_state = "holstered"
 	item_state = "backpack"

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

@@ -341,7 +341,7 @@
 
 /obj/item/gun/ballistic/revolver/doublebarrel/improvised/sawn
 	name = "sawn-off improvised shotgun"
-	desc = "A single-shot shotgun, better not miss"
+	desc = "A single-shot shotgun. Better not miss."
 	icon_state = "ishotgun"
 	item_state = "gun"
 	w_class = WEIGHT_CLASS_NORMAL

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

@@ -137,7 +137,7 @@
 
 /obj/item/gun/ballistic/shotgun/boltaction/enchanted/arcane_barrage
 	name = "arcane barrage"
-	desc = "Pew Pew Pew"
+	desc = "Pew Pew Pew."
 	fire_sound = 'sound/weapons/emitter.ogg'
 	pin = /obj/item/device/firing_pin/magic
 	icon_state = "arcane_barrage"