Replace tmpdir fixture with tmp_path

[rwedge]

Fixes #2151

[codecov]

Codecov Report

Merging #2344 (eedc610) into main (9d8c8f3) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main    #2344   +/-   ##
=======================================
  Coverage   99.41%   99.42%           
=======================================
  Files         310      310           
  Lines       19798    19773   -25     
=======================================
- Hits        19683    19660   -23     
+ Misses        115      113    -2     

Impacted Files	Coverage Δ
...utational_backend/test_calculate_feature_matrix.py	100.00% <100.00%> (ø)
featuretools/tests/conftest.py	100.00% <100.00%> (ø)
...eaturetools/tests/entityset_tests/test_plotting.py	100.00% <100.00%> (ø)
...etools/tests/entityset_tests/test_serialization.py	100.00% <100.00%> (+0.31%)	⬆️
...tests/primitive_tests/test_feature_descriptions.py	100.00% <100.00%> (ø)
...ests/primitive_tests/test_feature_serialization.py	100.00% <100.00%> (+0.38%)	⬆️
...s/tests/primitive_tests/test_feature_visualizer.py	100.00% <100.00%> (ø)

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