Fix Checkstyle violations

* Fix new Sonar smells

Author: artembilan

spring-integration-core/src/main/java/org/springframework/integration/channel/FluxMessageChannel.java

@@ -117,7 +117,7 @@ public void subscribeTo(Publisher<? extends Message<?>> publisher) {
 						.publishOn(this.scheduler)
 						.flatMap((message) ->
 								Mono.just(message)
-										.handle((messageToHandle, sink) -> sendReactiveMessage(messageToHandle))
+										.handle((messageToHandle, syncSink) -> sendReactiveMessage(messageToHandle))
 										.contextWrite(StaticMessageHeaderAccessor.getReactorContext(message)))
 						.contextCapture()
 						.subscribe());

spring-integration-core/src/main/java/org/springframework/integration/handler/advice/ContextHolderRequestHandlerAdvice.java

@@ -40,8 +40,6 @@ public class ContextHolderRequestHandlerAdvice extends AbstractRequestHandlerAdv
 
 	public final Runnable contextClearHook;
 
-	private boolean enableContextPropagation;
-
 	/**
 	 * Construct an instance based on the provided hooks.
 	 * @param valueProvider The key provider function.

spring-integration-zeromq/src/main/java/org/springframework/integration/zeromq/outbound/ZeroMqMessageHandler.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2020-2022 the original author or authors.
+ * Copyright 2020-2023 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.
@@ -16,7 +16,6 @@
 
 package org.springframework.integration.zeromq.outbound;
 
-import java.util.Arrays;
 import java.util.List;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.function.Consumer;