remove unused imports

[alexisdrakopoulos]

There are a few unused imports (though it is complicated as some seem unused but are used):
I ran the following to find them:

flake8 --select F401

Note to try to save time I ran autoflake which also removes some unused variables. I'm not sure how dangerous this is!

[codecov]

Codecov Report

Merging #2595 (e719983) into master (ebb6fde) will decrease coverage by 0.05%.
The diff coverage is 66.66%.

@@            Coverage Diff             @@
##           master    #2595      +/-   ##
==========================================
- Coverage   51.61%   51.55%   -0.06%     
==========================================
  Files          91       91              
  Lines       13147    13078      -69     
==========================================
- Hits         6786     6743      -43     
+ Misses       6361     6335      -26     

Impacted Files	Coverage Δ
shap/_explanation.py	54.60% <ø> (-0.28%)	⬇️
shap/actions/_optimizer.py	14.54% <ø> (-1.53%)	⬇️
shap/benchmark/_sequential.py	0.00% <0.00%> (ø)
shap/benchmark/experiments.py	0.00% <ø> (ø)
shap/benchmark/framework.py	0.00% <0.00%> (ø)
shap/benchmark/measures.py	0.00% <ø> (ø)
shap/benchmark/metrics.py	0.00% <ø> (ø)
shap/benchmark/models.py	0.00% <ø> (ø)
shap/explainers/_additive.py	28.20% <ø> (-5.13%)	⬇️
shap/explainers/_kernel.py	89.38% <ø> (-0.03%)	⬇️
... and 13 more

📣 Codecov can now indicate which changes are the most critical in Pull Requests. Learn more

[thatlittleboy]

Duplicated by #2943