Suppress deprecation warning in WebAsyncManagerTests

See gh-27959

Author: philwebb

spring-web/src/test/java/org/springframework/web/context/request/async/WebAsyncManagerTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 the original author or authors.
+ * Copyright 2002-2022 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -380,6 +380,7 @@ public Object call() throws Exception {
 	private static class SyncTaskExecutor extends SimpleAsyncTaskExecutor {
 
 		@Override
+		@SuppressWarnings("deprecation")
 		public void execute(Runnable task, long startTimeout) {
 			task.run();
 		}