Update ReactiveTypeHandlerTests due to deprecations in Reactor

spring-webmvc/src/test/java/org/springframework/web/servlet/mvc/method/annotation/ReactiveTypeHandlerTests.java

@@ -109,11 +109,11 @@ public class ReactiveTypeHandlerTests {
 	public void deferredResultSubscriberWithOneValue() throws Exception {
 
 		// Mono
-		MonoProcessor<String> mono = MonoProcessor.create();
+		MonoProcessor<String> mono = MonoProcessor.fromSink(Sinks.one());
 		testDeferredResultSubscriber(mono, Mono.class, forClass(String.class), () -> mono.onNext("foo"), "foo");
 
 		// Mono empty
-		MonoProcessor<String> monoEmpty = MonoProcessor.create();
+		MonoProcessor<String> monoEmpty = MonoProcessor.fromSink(Sinks.one());
 		testDeferredResultSubscriber(monoEmpty, Mono.class, forClass(String.class), monoEmpty::onComplete, null);
 
 		// RxJava Single