py/objgenerator: When throwing an object, don't make an exc instance.

Arguments to throw() for generators don't need to be exceptions.

py/objgenerator.c

@@ -193,7 +193,6 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_2(gen_instance_send_obj, gen_instance_send);
 STATIC mp_obj_t gen_instance_close(mp_obj_t self_in);
 STATIC mp_obj_t gen_instance_throw(size_t n_args, const mp_obj_t *args) {
     mp_obj_t exc = (n_args == 2) ? args[1] : args[2];
-    exc = mp_make_raise_obj(exc);
 
     mp_obj_t ret = gen_resume_and_raise(args[0], mp_const_none, exc);
     if (ret == MP_OBJ_STOP_ITERATION) {