Remove unused type: ignore statements

[jklaise]

This PR adds the mypy options warn_unused_ignores = True and warn_redundant_casts = True and fixes the resulting errors. This is motivated because type: ignore statements can become stale as newer versions of mypy fix bugs and libraries against which we typecheck ship typing stubs and fix bugs therein (e.g. numpy), see more here: https://mypy.readthedocs.io/en/stable/command_line.html#cmdoption-mypy-warn-unused-ignores

Will open a similar PR for alibi-detect after SeldonIO/alibi-detect#738.

@ascillitoe @mauicv FYI

[ascillitoe]

Makes sense!

[jklaise]

Not entirely unexpected, but there's some complications with running this on older python versions which have older dependencies (e.g. numpy) which may not allow removing type: ignore or, indeed, suggest removing ones that shouldn't be removed in newer python versions... https://github.com/SeldonIO/alibi/actions/runs/4173451223/jobs/7225790896

See discussion: python/mypy#8823, not this is slightly different as we don't check in our code the current Python version, but still may be relevant.

[ascillitoe]

Perhaps controversial, but do we actually care about mypy and flake8 passing for older Python versions. One could argue that its better for our codebase to be fully mypy and flake8 compliant on our most recent supported Python version, rather than include additional complexity to get these checks passing for Python versions that are close to EoL? We could factor out the mypy/flake8 checks to a separate workflow that is only run on ubuntu-latest, 3.10 for example...

[jklaise]

I was thinking similarly, need to think a bit more about implications.

[codecov]

Codecov Report

Merging #874 (e324583) into master (9a4c0bb) will not change coverage.
The diff coverage is 74.50%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #874   +/-   ##
=======================================
  Coverage   85.28%   85.28%           
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  Files          74       74           
  Lines        8832     8832           
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  Hits         7532     7532           
  Misses       1300     1300           

Impacted Files	Coverage Δ
alibi/explainers/backends/pytorch/cfrl_base.py	28.75% <0.00%> (ø)
alibi/explainers/permutation_importance.py	97.09% <0.00%> (ø)
alibi/saving.py	83.75% <0.00%> (ø)
alibi/utils/visualization.py	48.10% <0.00%> (ø)
alibi/explainers/cfproto.py	75.57% <50.00%> (ø)
alibi/explainers/cem.py	79.31% <60.00%> (ø)
alibi/confidence/trustscore.py	86.07% <100.00%> (ø)
alibi/datasets/default.py	93.47% <100.00%> (ø)
alibi/explainers/anchors/anchor_image.py	93.12% <100.00%> (ø)
alibi/explainers/anchors/anchor_tabular.py	89.57% <100.00%> (ø)
... and 7 more