Replace ensure_future with create_task

[dvora-h]

Pull Request check-list

Please make sure to review and check all of these items:

• Does $ tox pass with this change (including linting)?
• Do the CI tests pass with this change (enable it first in your forked repo and wait for the github action build to finish)?
• Is the new or changed code fully tested?
• Is a documentation update included (if this change modifies existing APIs, or introduces new ones)?
• Is there an example added to the examples folder (if applicable)?
• Was the change added to CHANGES file?

NOTE: these things are not required to open a PR and can be done
afterwards / while the PR is open.

Description of change

As part of #2306

[codecov-commenter]

Codecov Report

Merging #2311 (efea0c4) into master (f9f9d06) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #2311   +/-   ##
=======================================
  Coverage   92.06%   92.07%           
=======================================
  Files         109      109           
  Lines       28241    28238    -3     
=======================================
  Hits        25999    25999           
+ Misses       2242     2239    -3     

Impacted Files	Coverage Δ
redis/commands/cluster.py	93.64% <ø> (ø)
redis/asyncio/cluster.py	90.28% <100.00%> (ø)
tests/test_asyncio/compat.py	100.00% <100.00%> (+9.09%)	⬆️
tests/test_cluster.py	96.85% <0.00%> (+0.11%)	⬆️

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