Remove outdated pandas workaround code in feature_set_calculator.py

[thehomebrewnerd]

Remove outdated pandas workaround code in feature_set_calculator.py

Closes #1711

The pandas issue that caused the code to be added appears to be resolved in more recent pandas releases, so this code is no longer necessary. See #1711 for more details.

[gsheni]

@thehomebrewnerd Will you need to bump up the min pandas version?

[thehomebrewnerd]

@thehomebrewnerd Will you need to bump up the min pandas version?

No, this was fixed prior to pandas 1.3.0 which is our current min version.

[codecov]

Codecov Report

Merging #1906 (efe4848) into main (e86c353) will increase coverage by 0.09%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #1906      +/-   ##
==========================================
+ Coverage   98.68%   98.77%   +0.09%     
==========================================
  Files         148      148              
  Lines       16355    16352       -3     
==========================================
+ Hits        16140    16152      +12     
+ Misses        215      200      -15     

Impacted Files	Coverage Δ
...s/computational_backends/feature_set_calculator.py	98.69% <ø> (+0.24%)	⬆️
...computational_backends/calculate_feature_matrix.py	100.00% <0.00%> (+0.83%)	⬆️
...utational_backend/test_calculate_feature_matrix.py	100.00% <0.00%> (+1.19%)	⬆️

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[rwedge]

Looks good!