chore(cmd): improve the exit-zero option help message

[gg-jonathangriffe]

Context

The help message for the exit-zero option can be slightly misleading, as one could understand that it will make the command exit with the 0 exit code, regardless of the error raised.

What has been done

The exit-zero option help message was modified to make it clear it only applies when a secret is detected.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.86%. Comparing base (7d85eb1) to head (4ae2c58).
Report is 13 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1041      +/-   ##
==========================================
- Coverage   92.09%   91.86%   -0.24%     
==========================================
  Files         181      181              
  Lines        7755     7755              
==========================================
- Hits         7142     7124      -18     
- Misses        613      631      +18     

Flag	Coverage Δ
unittests	91.86% <ø> (-0.24%)	⬇️

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[mathieubellon]

LGTM @sevbch