Tag validation errors for non-relevant messages

[masih]

Add the missing custom tag for ErrValidationNotRelevant type as invalid_not_relevant.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 69.38%. Comparing base (483e58b) to head (0ccc1a6).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #766      +/-   ##
==========================================
- Coverage   69.65%   69.38%   -0.27%     
==========================================
  Files          74       74              
  Lines        7551     7553       +2     
==========================================
- Hits         5260     5241      -19     
- Misses       1877     1895      +18     
- Partials      414      417       +3     

Files with missing lines	Coverage Δ
gpbft/metrics.go	62.06% <100.00%> (-4.60%)	⬇️

... and 3 files with indirect coverage changes