[flang][runtime] Fix bad instance of std::optional in runtime (#148724)

The runtime needs to use common::optional, not std::optional.

Author: klausler

flang-rt/include/flang-rt/runtime/work-queue.h

@@ -307,7 +307,7 @@ class DestroyTicket : public ImmediateTicketRunner<DestroyTicket>,
 
 private:
   bool finalize_{false};
-  std::optional<SubscriptValue> fixedStride_;
+  common::optional<SubscriptValue> fixedStride_;
 };
 
 // Implements general intrinsic assignment