[mlir] Fix opaque struct typedef in AsyncRuntime header

mlir/include/mlir/ExecutionEngine/AsyncRuntime.h

 #define MLIR_ASYNCRUNTIME_DEFINE_FUNCTIONS
 #endif // _WIN32
 
 //===----------------------------------------------------------------------===//
 // Async runtime API.
 //===----------------------------------------------------------------------===//
 
 // Runtime implementation of `async.token` data type.
-typedef struct AsyncToken MLIR_AsyncToken;
+typedef struct AsyncToken AsyncToken;
 
 // Runtime implementation of `async.group` data type.
-typedef struct AsyncGroup MLIR_AsyncGroup;
+typedef struct AsyncGroup AsyncGroup;
 
 // Async runtime uses LLVM coroutines to represent asynchronous tasks. Task
 // function is a coroutine handle and a resume function that continue coroutine
 // execution from a suspension point.
 using CoroHandle = void *;           // coroutine handle
 using CoroResume = void (*)(void *); // coroutine resume function
 
 // Async runtime uses reference counting to manage the lifetime of async values