fix get_internal word register names

seems previous commits broke the return

lib/slot_machine/macro/get_internal_word.rb

@@ -2,11 +2,8 @@ module SlotMachine
   class GetInternalWord < Macro
     def to_risc(compiler)
       compiler.builder(compiler.source).build do
-        object! << message[:receiver]
-        integer! << message[:arg1] #"at" is at index 0
-        integer.reduce_int
-        object << object[integer]
-        message[:return_value] << object
+        integer = message[:arg1].to_reg.reduce_int(false)
+        message[:return_value] << message[:receiver][integer]
       end
     end
   end