Apply clang-tidy fixes for llvm-include-order in Parser.cpp (NFC)

Author: joker-eph

mlir/lib/Tools/PDLL/Parser/Parser.cpp

@@ -31,8 +31,8 @@
 #include "llvm/Support/ScopedPrinter.h"
 #include "llvm/TableGen/Error.h"
 #include "llvm/TableGen/Parser.h"
-#include <string>
 #include <optional>
+#include <string>
 
 using namespace mlir;
 using namespace mlir::pdll;