Use tmp_path for temp file in test

[svank]

A small tweak for the tests---using a tmp dir for the tests that save and load files. Without this change, one of these tests would sometimes fail when I used pytest-xdist to run tests across multiple cores, I assume because they were trampling each other's output files.

I also noticed that test_create_array_corrector, which I've re-named test_save_load_array_corrector, was overwriting another test in that file also called test_create_array_corrector.

[codecov-commenter]

Codecov Report

Patch coverage: 100.00% and project coverage change: +0.39 🎉

Comparison is base (fa87007) 93.39% compared to head (1523c5f) 93.79%.

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Additional details and impacted files

@@            Coverage Diff             @@
##             main      #24      +/-   ##
==========================================
+ Coverage   93.39%   93.79%   +0.39%     
==========================================
  Files           9        9              
  Lines         757      757              
==========================================
+ Hits          707      710       +3     
+ Misses         50       47       -3     

Impacted Files	Coverage Δ
tests/test_corrector.py	95.39% <100.00%> (+1.97%)	⬆️

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[jmbhughes]

This is a good catch. I note that related to #25 we want to get rid of the pickling, but that's a separate thing to resolve.