Replace use of deprecated Reactor MonoProcessor in tests

Fixes gh-23627

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/web/reactive/server/AbstractReactiveWebServerFactoryTests.java

@@ -45,7 +45,6 @@ import org.awaitility.Awaitility;
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.Test;
 import reactor.core.publisher.Mono;
-import reactor.core.publisher.MonoProcessor;
 import reactor.core.publisher.Sinks;
 import reactor.netty.NettyPipeline;
 import reactor.netty.http.client.HttpClient;
@@ -499,7 +498,7 @@ public abstract class AbstractReactiveWebServerFactoryTests {
 
 	protected static class BlockingHandler implements HttpHandler {
 
-		private final BlockingQueue<MonoProcessor<Void>> processors = new ArrayBlockingQueue<>(10);
+		private final BlockingQueue<Sinks.Empty<Void>> processors = new ArrayBlockingQueue<>(10);
 
 		private volatile boolean blocking = true;
 
@@ -510,8 +509,8 @@ public abstract class AbstractReactiveWebServerFactoryTests {
 		@Override
 		public Mono<Void> handle(ServerHttpRequest request, ServerHttpResponse response) {
 			if (this.blocking) {
-				Sinks.One<Void> completion = Sinks.one();
-				this.processors.add(MonoProcessor.fromSink(completion));
+				Sinks.Empty<Void> completion = Sinks.empty();
+				this.processors.add(completion);
 				return completion.asMono().then(Mono.empty());
 			}
 			return Mono.empty();
@@ -519,8 +518,8 @@ public abstract class AbstractReactiveWebServerFactoryTests {
 
 		public void completeOne() {
 			try {
-				MonoProcessor<Void> processor = this.processors.take();
-				processor.onComplete();
+				Sinks.Empty<Void> processor = this.processors.take();
+				processor.tryEmitEmpty();
 			}
 			catch (InterruptedException ex) {
 				Thread.currentThread().interrupt();
@@ -535,7 +534,7 @@ public abstract class AbstractReactiveWebServerFactoryTests {
 
 		public void stopBlocking() {
 			this.blocking = false;
-			this.processors.forEach(MonoProcessor::onComplete);
+			this.processors.forEach(Sinks.Empty::tryEmitEmpty);
 		}
 
 	}