Disable deprecated flake8-mypy Python tox check

[jdeamicis]

Description of changes

• Disable deprecated flake8-mypy Python tox check, which caused problems in the GitHub actions on the repository.

References

• Disable deprecated flake8-mypy Python tox check aws-parallelcluster#5753
• Disable deprecated flake8-mypy Python tox check aws-parallelcluster-cookbook#2493

Checklist

• Make sure you are pointing to the right branch.
• If you're creating a patch for a branch other than develop add the branch name as prefix in the PR title (e.g. [release-3.6]).
• Check all commits' messages are clear, describing what and why vs how.
• Make sure to have added unit tests or integration tests to cover the new/modified code.
• Check if documentation is impacted by this change.

Please review the guidelines for contributing and Pull Request Instructions.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov]

Codecov Report

All modified lines are covered by tests ✅

Comparison is base (3ecda34) 89.44% compared to head (7fa28f7) 89.44%.

Additional details and impacted files

@@             Coverage Diff              @@
##           release-3.7     #572   +/-   ##
============================================
  Coverage        89.44%   89.44%           
============================================
  Files               16       16           
  Lines             2633     2633           
============================================
  Hits              2355     2355           
  Misses             278      278           

Flag	Coverage Δ
unittests	89.44% <ø> (ø)

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