fetch minisign from homebrew instead of custom ppa

[bobcallaway]

this should remove some flakiness from the builds which are failing to download minisign from the custom ubuntu ppa

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 49.88%. Comparing base (488eb97) to head (2cf9905).
Report is 278 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #2329       +/-   ##
===========================================
- Coverage   66.46%   49.88%   -16.58%     
===========================================
  Files          92      192      +100     
  Lines        9258    24683    +15425     
===========================================
+ Hits         6153    12314     +6161     
- Misses       2359    11278     +8919     
- Partials      746     1091      +345     

Flag	Coverage Δ
e2etests	46.52% <ø> (-1.04%)	⬇️
unittests	41.90% <ø> (-5.78%)	⬇️

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