stop duping values from Hash#values

src/hash.c

@@ -1043,8 +1043,6 @@ mrb_hash_values(mrb_state *mrb, mrb_value hash)
   for (k = kh_begin(h); k != kh_end(h); k++) {
     if (kh_exist(h, k)){
       mrb_value v = kh_value(h,k);
-      if ( !mrb_special_const_p(v) )
-        v = mrb_obj_dup(mrb, v);
       mrb_ary_push(mrb, ary, v);
     }
   }