Remove unused import statements.

Author: us

tensorflow_datasets/core/dataset_builder_test.py

@@ -22,7 +22,6 @@
 import os
 
 from absl.testing import absltest
-from absl.testing import parameterized
 import numpy as np
 import tensorflow as tf
 from tensorflow_datasets import testing

tensorflow_datasets/core/tfrecords_reader.py

@@ -22,7 +22,6 @@
 import functools
 import itertools
 import math
-import os
 import re
 
 import attr