Apply clang-tidy fixes for llvm-qualified-auto in PredicateTree.cpp (NFC)

Author: joker-eph

mlir/lib/Conversion/PDLToPDLInterp/PredicateTree.cpp

@@ -856,7 +856,7 @@ static void foldSwitchToBool(std::unique_ptr<MatcherNode> &node) {
     // If the node only contains one child, collapse it into a boolean predicate
     // node.
     if (children.size() == 1) {
-      auto childIt = children.begin();
+      auto *childIt = children.begin();
       node = std::make_unique<BoolNode>(
           node->getPosition(), node->getQuestion(), childIt->first,
           std::move(childIt->second), std::move(node->getFailureNode()));