Remove Netty 5 support

Closes gh-34345

buildSrc/src/main/java/org/springframework/build/TestConventions.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2024 the original author or authors.
+ * Copyright 2002-2025 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.
@@ -54,10 +54,7 @@ private void configureTests(Project project, Test test) {
 		test.include("**/*Tests.class", "**/*Test.class");
 		test.setSystemProperties(Map.of(
 				"java.awt.headless", "true",
-				"io.netty.leakDetection.level", "paranoid",
-				"io.netty5.leakDetectionLevel", "paranoid",
-				"io.netty5.leakDetection.targetRecords", "32",
-				"io.netty5.buffer.lifecycleTracingEnabled", "true"
+				"io.netty.leakDetection.level", "paranoid"
 		));
 		if (project.hasProperty("testGroups")) {
 			test.systemProperty("testGroups", project.getProperties().get("testGroups"));

framework-platform/framework-platform.gradle

@@ -10,7 +10,6 @@ dependencies {
 	api(platform("com.fasterxml.jackson:jackson-bom:2.18.2"))
 	api(platform("io.micrometer:micrometer-bom:1.14.4"))
 	api(platform("io.netty:netty-bom:4.1.117.Final"))
-	api(platform("io.netty:netty5-bom:5.0.0.Alpha5"))
 	api(platform("io.projectreactor:reactor-bom:2024.0.3"))
 	api(platform("io.rsocket:rsocket-bom:1.1.5"))
 	api(platform("org.apache.groovy:groovy-bom:4.0.24"))
@@ -49,7 +48,6 @@ dependencies {
 		api("de.bechte.junit:junit-hierarchicalcontextrunner:4.12.2")
 		api("io.micrometer:context-propagation:1.1.1")
 		api("io.mockk:mockk:1.13.4")
-		api("io.projectreactor.netty:reactor-netty5-http:2.0.0-M3")
 		api("io.projectreactor.tools:blockhound:1.0.8.RELEASE")
 		api("io.r2dbc:r2dbc-h2:1.0.0.RELEASE")
 		api("io.r2dbc:r2dbc-spi-test:1.0.0.RELEASE")

spring-core/spring-core.gradle

@@ -77,7 +77,6 @@ dependencies {
 	compileOnly("org.graalvm.sdk:graal-sdk")
 	optional("io.micrometer:context-propagation")
 	optional("io.netty:netty-buffer")
-	optional("io.netty:netty5-buffer")
 	optional("io.projectreactor:reactor-core")
 	optional("io.reactivex.rxjava3:rxjava")
 	optional("io.smallrye.reactive:mutiny")