BE-714 | Fix candidate_routes_compute_duration gauge call (#638)

Author: deividaspetraitis

router/usecase/router_usecase.go

@@ -694,7 +694,7 @@ func (r *routerUseCaseImpl) handleCandidateRoutes(ctx context.Context, tokenIn s
 
 		r.logger.Info("calculated routes", zap.Int("num_routes", len(candidateRoutes.Routes)), zap.Duration("duration", time.Since(start)))
 
-		domain.SQSCandidateRoutesComputeDurationGauge.Add(float64(time.Since(start).Milliseconds()))
+		domain.SQSCandidateRoutesComputeDurationGauge.Set(float64(time.Since(start).Milliseconds()))
 
 		// Persist routes
 		if !candidateRouteSearchOptions.DisableCache {