Removes unused pressure_resistance variable.

This is used with FEA not ZAS

Though it's kind of funny to look at what some of these values were set at.
(For reference: ONE_ATMOSPHERE = 101.325)

code/modules/paperwork/folders.dm

@@ -4,7 +4,6 @@
 	icon = 'icons/obj/bureaucracy.dmi'
 	icon_state = "folder"
 	w_class = 2
-	pressure_resistance = 2
 
 /obj/item/weapon/folder/blue
 	desc = "A blue folder."

code/modules/paperwork/paper.dm

@@ -14,7 +14,6 @@
 	throw_range = 1
 	throw_speed = 1
 	layer = 4
-	pressure_resistance = 1
 	slot_flags = SLOT_HEAD
 	body_parts_covered = HEAD
 	attack_verb = list("bapped")

code/modules/paperwork/paper_bundle.dm

@@ -9,7 +9,6 @@
 	throw_range = 2
 	throw_speed = 1
 	layer = 4
-	pressure_resistance = 1
 	attack_verb = list("bapped")
 	var/page = 1    // current page
 	var/list/pages = list()  // Ordered list of pages as they are to be displayed. Can be different order than src.contents.
@@ -240,4 +239,4 @@
 	if(photo)
 		desc += "\nThere is a photo attached to it."
 	overlays += image('icons/obj/bureaucracy.dmi', "clip")
-	return
+	return

code/modules/paperwork/paperbin.dm

@@ -7,7 +7,6 @@
 	w_class = 3
 	throw_speed = 3
 	throw_range = 7
-	pressure_resistance = 10
 	layer = OBJ_LAYER - 0.1
 	var/amount = 30					//How much paper is in the bin.
 	var/list/papers = new/list()	//List of papers put in the bin for reference.

code/modules/paperwork/pen.dm

@@ -22,7 +22,6 @@
 	throw_range = 15
 	matter = list(DEFAULT_WALL_MATERIAL = 10)
 	var/colour = "black"	//what colour the ink is!
-	pressure_resistance = 2
 
 
 /obj/item/weapon/pen/blue

code/modules/paperwork/stamps.dm

@@ -9,7 +9,6 @@
 	throw_speed = 7
 	throw_range = 15
 	matter = list(DEFAULT_WALL_MATERIAL = 60)
-	pressure_resistance = 2
 	attack_verb = list("stamped")
 
 /obj/item/weapon/stamp/captain
@@ -73,4 +72,4 @@
 
 		if(chosen_stamp)
 			name = chosen_stamp.name
-			icon_state = chosen_stamp.icon_state
+			icon_state = chosen_stamp.icon_state