Fixed "use a reference" warning

src/scheduler/Scheduler.cpp

@@ -243,10 +243,10 @@ void Aidge::SequentialScheduler::generateScheduling(bool verbose) {
             // its childs become consumers.
             bool isProducer = false;
             for (IOIndex_t outId = 0; outId < consumer->nbOutputs(); ++outId) {
-                for (const auto child : consumer->getChildren(outId)) {
+                for (const auto& child : consumer->getChildren(outId)) {
                     if (child) {
                         IOIndex_t inputIdx = 0;
-                        for (const auto childParent : child->getParents()) {
+                        for (const auto& childParent : child->getParents()) {
                             if (childParent == consumer) {
                                 if (consumer->getOperator()->getNbProducedData(outId) > child->getOperator()->getNbConsumedData(inputIdx)) {
                                     isProducer = true;