Update pythonpackage.yml to limit one test result upload and one code coverage upload

[gaugup]

This fixes the issue where the python PR gate was failing during upload of unit test results for python 3.6. Now limiting test result upload and code coverage upload for linux build with python 3.8.

[github-actions]

Unit Test Results

    1 files  ±0      1 suites  ±0   9m 54s ⏱️ - 5m 9s
242 tests ±0  237 ✔️ ±0  5 💤 ±0  0 ❌ ±0 

Results for commit a25af23. ± Comparison against base commit bb9df91.

♻️ This comment has been updated with latest results.

[codecov-commenter]

Codecov Report

Merging #282 (a25af23) into master (bb9df91) will decrease coverage by 0.10%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #282      +/-   ##
==========================================
- Coverage   71.27%   71.17%   -0.11%     
==========================================
  Files          26       26              
  Lines        3440     3438       -2     
==========================================
- Hits         2452     2447       -5     
- Misses        988      991       +3     

Flag	Coverage Δ
unittests	71.17% <ø> (-0.11%)	⬇️

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Impacted Files	Coverage Δ
dice_ml/explainer_interfaces/explainer_base.py	88.41% <0.00%> (-1.13%)	⬇️
dice_ml/explainer_interfaces/dice_genetic.py	95.96% <0.00%> (-0.02%)	⬇️
dice_ml/explainer_interfaces/dice_tensorflow1.py	0.00% <0.00%> (ø)

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