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/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