chore(get-modflow): workaround broken local CA trust store

[wpbonelli]

Motivated by CI errors caused by unreliably provisioned GitHub Actions runners

[codecov]

Codecov Report

❌ Patch coverage is 35.29412% with 11 lines in your changes missing coverage. Please review.
✅ Project coverage is 72.7%. Comparing base (556c088) to head (e202f99).
⚠️ Report is 198 commits behind head on develop.

Files with missing lines	Patch %	Lines
flopy/utils/get_modflow.py	35.2%	11 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #2806      +/-   ##
===========================================
+ Coverage     55.5%    72.7%   +17.2%     
===========================================
  Files          644      661      +17     
  Lines       124135   133020    +8885     
===========================================
+ Hits         68947    96834   +27887     
+ Misses       55188    36186   -19002     

Files with missing lines	Coverage Δ
flopy/utils/get_modflow.py	26.2% <35.2%> (-37.5%)	⬇️

... and 582 files with indirect coverage changes

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