chore(frost-core): fix dead_code warning

[StackOverflowExcept1on]

This PR fixes dead_code warning. I get this error when reusing frost-core in roast-core.

$ cargo clippy --release -p frost-core --no-default-features -F internals

    Checking frost-core v2.0.0-rc.0 (/tmp/frost/frost-core)
warning: function `detect_cheater` is never used
   --> frost-core/src/lib.rs:637:4
    |
637 | fn detect_cheater<C: Ciphersuite>(
    |    ^^^^^^^^^^^^^^
    |
    = note: `#[warn(dead_code)]` on by default

[StackOverflowExcept1on]

@conradoplg

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.45%. Comparing base (5f4ac6e) to head (5cf2646).
Report is 53 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #748      +/-   ##
==========================================
- Coverage   82.18%   81.45%   -0.73%     
==========================================
  Files          31       34       +3     
  Lines        3188     3289     +101     
==========================================
+ Hits         2620     2679      +59     
- Misses        568      610      +42     

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