Big Animals MAI engine: don't load two unused libraries

data/ai/micro_ais/ais/mai_big_animals_engine.lua

@@ -3,9 +3,7 @@ return {
         local engine = existing_engine or {}
 
         local H = wesnoth.require "lua/helper.lua"
-        local W = H.set_wml_action_metatable {}
         local AH = wesnoth.require "ai/lua/ai_helper.lua"
-        local BC = wesnoth.require "ai/lua/battle_calcs.lua"
         local LS = wesnoth.require "lua/location_set.lua"
 
         function engine:mai_animals_big_eval(cfg)