change "Error:" to "find:" + Testcase fix

[Crypto-Darth]

Changed the error format of
Error: .......
to
find: .......
to match GNU and also help pass testsuite.

Also fixed an error message which was failing test in GNU Testsuite and it is now passing (tests/find/user-group-max.sh)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 87.70%. Comparing base (a571de6) to head (bb592d7).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #534   +/-   ##
=======================================
  Coverage   87.70%   87.70%           
=======================================
  Files          31       31           
  Lines        6887     6891    +4     
  Branches      324      324           
=======================================
+ Hits         6040     6044    +4     
  Misses        616      616           
  Partials      231      231           

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[Crypto-Darth]

Thank you :)