disable fuzzer on policy evaluation code path

[bobcallaway]

EvaluatePolicyAgainstJSON is a thin wrapper around calling cue or rego and we're getting fuzzing reports that aren't really bugs in cosign.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 36.89%. Comparing base (2ef6022) to head (e0c4f77).
Report is 298 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4051      +/-   ##
==========================================
- Coverage   40.10%   36.89%   -3.22%     
==========================================
  Files         155      209      +54     
  Lines       10044    13352    +3308     
==========================================
+ Hits         4028     4926     +898     
- Misses       5530     7799    +2269     
- Partials      486      627     +141     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.