Use std::optional instead of llvm::Optional

Author: devajithvs

mlir/lib/Tools/mlir-query/MlirQueryMain.cpp

@@ -89,7 +89,7 @@ LogicalResult mlir::mlirQueryMain(int argc, char **argv, MLIRContext &context) {
   LE.setListCompleter([&QS](StringRef Line, size_t Pos) {
     return QueryParser::complete(Line, Pos, QS);
   });
-  while (llvm::Optional<std::string> Line = LE.readLine()) {
+  while (std::optional<std::string> Line = LE.readLine()) {
     QueryRef Q = QueryParser::parse(*Line, QS);
     Q->run(llvm::outs(), QS);
     llvm::outs().flush();

mlir/lib/Tools/mlir-query/Query.h

@@ -12,7 +12,6 @@
 #include "Parser.h"
 #include "mlir/IR/Matchers.h"
 #include "llvm/ADT/IntrusiveRefCntPtr.h"
-#include "llvm/ADT/Optional.h"
 #include "llvm/ADT/Twine.h"
 #include <string>