[NFC] address a compiler warning about auto& being ignored

Author: kavon

lib/SILOptimizer/Mandatory/DefiniteInitialization.cpp

@@ -967,7 +967,7 @@ void LifetimeChecker::injectActorHops() {
 
     AvailabilitySet inSet(outSet.size());
     auto const &predecessors = block.getPredecessorBlocks();
-    for (const auto &pred : predecessors)
+    for (auto *pred : predecessors)
       inSet.mergeIn(getBlockInfo(pred).OutAvailability);
 
     if (inSet.isAllYes()) {