Fix shipyard store not selling class 2 Military Drive

Class 2 military drives require "MILITARY" tech level, which under the hood is
interpreted as tech-level 11 (because that's how Frontier implemented it).
Higher military drives are available at higher tech levels. Code had a bug
where in stations of higher tech level than "MILITARY", you could only buy
military drive of class 1, 3, and 4, but not military drive class 2.

data/pigui/libs/ship-equipment.lua

@@ -118,7 +118,7 @@ local hasTech = function (station, e)
 
 	if type(equip_tech_level) == "string" then
 		if equip_tech_level == "MILITARY" then
-			return station.techLevel == 11
+			equip_tech_level = 11
 		else
 			error("Unknown tech level:\t"..equip_tech_level)
 		end