Remove support for Python 3.8

[fealho]

CU-86b75wvc5, Resolve #493.

[sdv-team]

Task linked: CU-86b75wvc5 Copulas - Remove support for Python 3.8 #493

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.13%. Comparing base (bdf7d3c) to head (c787b03).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #494      +/-   ##
==========================================
- Coverage   90.14%   90.13%   -0.02%     
==========================================
  Files          29       29              
  Lines        1826     1824       -2     
==========================================
- Hits         1646     1644       -2     
  Misses        180      180              

Flag	Coverage Δ
integration	79.71% <100.00%> (-0.03%)	⬇️
unit	86.84% <100.00%> (-0.02%)	⬇️

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