Fix dnn_trainer trying to decrease the learning rate (#2442)

dlib/dnn/trainer.h

@@ -1061,7 +1061,7 @@ namespace dlib
                     // lower one instead.
                     if (prob_loss_increasing_thresh >= prob_loss_increasing_thresh_max_value)
                     {
-                        if (verbose)
+                        if (verbose && learning_rate_shrink != 1)
                             std::cout << "(and while at it, also shrinking the learning rate)" << std::endl;
 
                         learning_rate = learning_rate_shrink * learning_rate;