fix misleading error message for when thresholds not provided

src/utils.hpp

@@ -113,7 +113,7 @@ namespace evalhyd
                               metric) != threshold_metrics.end())
                     if (thresholds.size() < 1)
                         throw std::runtime_error(
-                                "missing parameter 'thresholds' required to "
+                                "missing thresholds *q_thr* required to "
                                 "compute " + metric
                         );
             }