message: Fix the serialization test for CacheDatasetOp
diff: @@ -85,7 +85,6 @@ class CacheDatasetSerializationTest(
  ds_fn, [5], 8, verify_exhausted=False, save_checkpoint_at_end=False)
  self.assertSequenceEqual(outputs, range(8))
  - if is_memory:
  outputs = outputs[:5]
  outputs.extend(
  self.gen_outputs(
  @@ -94,15 +93,6 @@ class CacheDatasetSerializationTest(
  ckpt_saved=True,
  verify_exhausted=False))
  self.assertSequenceEqual(outputs, self.expected_outputs())
  - else:
  - # Restoring from checkpoint and running GetNext should return
  - # `AlreadExistsError` now because the lockfile already exists.
  - with self.assertRaises(errors.AlreadyExistsError):
  - self.gen_outputs(
  - ds_fn, [],
  - self.num_outputs - 5,
  - ckpt_saved=True,
  - verify_exhausted=False)
  @parameterized.named_parameters(
  ('Memory', True),
  