disable fail-fast behavior on CI tests

[rwedge]

Disable the fail-fast strategy on our unit tests, which is cancelling jobs if a job in the same test matrix has failed (currently if the py38 optional unit tests fail, the py37 and py36 optionals will be cancelled). I'd prefer to have the tests continue to so we'll know if there are issues with the other environments we're testing on.

[codecov]

Codecov Report

Merging #1386 (6cd4ca4) into main (ca05bee) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main    #1386   +/-   ##
=======================================
  Coverage   98.58%   98.58%           
=======================================
  Files         135      135           
  Lines       14546    14578   +32     
=======================================
+ Hits        14340    14372   +32     
  Misses        206      206           

Impacted Files	Coverage Δ
featuretools/entityset/deserialize.py	100.00% <100.00%> (ø)
featuretools/tests/conftest.py	100.00% <100.00%> (ø)
featuretools/tests/entityset_tests/test_es.py	100.00% <100.00%> (ø)
...s/tests/primitive_tests/test_transform_features.py	98.80% <100.00%> (+0.03%)	⬆️

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[thehomebrewnerd]

Looks good!