Update files from the datasets library (from 1.6.0)

Release notes: https://github.com/huggingface/datasets/releases/tag/1.6.0

c4.py

@@ -16,7 +16,6 @@
 # Lint as: python3
 """C4 dataset based on Common Crawl."""
 
-from __future__ import absolute_import, division, print_function
 
 import json
 import os

c4_utils.py

@@ -16,7 +16,6 @@
 # Lint as: python3
 """Utilities for generating the C4 dataset."""
 
-from __future__ import absolute_import, division, print_function
 
 import functools
 import gzip