Refactor deprecated randomNonce() with Salter().qb64

[rubelhassan]

Issue keripy #739

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.83%. Comparing base (caad67b) to head (62b6ad0).
Report is 7 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #241      +/-   ##
==========================================
+ Coverage   92.82%   92.83%   +0.01%     
==========================================
  Files          37       37              
  Lines        6982     6995      +13     
==========================================
+ Hits         6481     6494      +13     
  Misses        501      501              

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