Use llvm::less_first and llvm::less_second (NFC)

GitOrigin-RevId: acf648b5e91b6ccbb6e29a6db344e8d8ae0fbdb7
diff --git a/source/Plugins/ExpressionParser/Clang/ClangASTSource.cpp b/source/Plugins/ExpressionParser/Clang/ClangASTSource.cpp
index f8443d6..26775e7 100644
--- a/source/Plugins/ExpressionParser/Clang/ClangASTSource.cpp
+++ b/source/Plugins/ExpressionParser/Clang/ClangASTSource.cpp
@@ -1430,9 +1430,7 @@
   std::vector<PairType> sorted_items;
   sorted_items.reserve(source_map.size());
   sorted_items.assign(source_map.begin(), source_map.end());
-  llvm::sort(sorted_items, [](const PairType &lhs, const PairType &rhs) {
-    return lhs.second < rhs.second;
-  });
+  llvm::sort(sorted_items, llvm::less_second());
 
   for (const auto &item : sorted_items) {
     DeclFromUser<D> user_decl(const_cast<D *>(item.first));