[AIRFLOW-6840] Bump up version of future

[yuqian90]

NOTE: This PR is against branch v1-10-test

The future package was removed in master, but v1-10-test still needs it. Bumping up the version makes it easier to migrate to python3.8. More specifically this is the change that should be picked up:

• Fix collections.abc import for py38+
  See https://github.com/PythonCharmers/python-future/blob/master/docs/whatsnew.rst

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Issue link: AIRFLOW-6840

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• Description above provides context of the change
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[codecov-io]

Codecov Report

Merging #7471 into v1-10-test will increase coverage by <.01%.
The diff coverage is n/a.

@@              Coverage Diff               @@
##           v1-10-test    #7471      +/-   ##
==============================================
+ Coverage       81.63%   81.64%   +<.01%     
==============================================
  Files             529      529              
  Lines           36437    36437              
==============================================
+ Hits            29747    29749       +2     
+ Misses           6690     6688       -2

Impacted Files	Coverage Δ
airflow/operators/postgres_operator.py	100% <0%> (ø)	⬆️
airflow/operators/mysql_operator.py	100% <0%> (ø)	⬆️
airflow/operators/mysql_to_hive.py	100% <0%> (ø)	⬆️
airflow/operators/generic_transfer.py	100% <0%> (ø)	⬆️
airflow/contrib/kubernetes/volume_mount.py	100% <0%> (ø)	⬆️
airflow/hooks/hdfs_hook.py	92.5% <0%> (ø)	⬆️
airflow/contrib/kubernetes/volume.py	100% <0%> (ø)	⬆️
airflow/contrib/kubernetes/pod_launcher.py	92.48% <0%> (ø)	⬆️
airflow/security/kerberos.py	75.55% <0%> (ø)	⬆️
airflow/contrib/kubernetes/pod_generator.py	87.5% <0%> (ø)	⬆️
... and 25 more

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