Fix Jetty multipart client support with Java 25

Closes gh-35531

framework-platform/framework-platform.gradle

@@ -15,7 +15,7 @@ dependencies {
 	api(platform("org.apache.groovy:groovy-bom:5.0.1"))
 	api(platform("org.apache.logging.log4j:log4j-bom:2.25.1"))
 	api(platform("org.assertj:assertj-bom:3.27.6"))
-	api(platform("org.eclipse.jetty:jetty-bom:12.1.2"))
+	api(platform("org.eclipse.jetty:jetty-bom:12.1.3"))
 	api(platform("org.eclipse.jetty.ee11:jetty-ee11-bom:12.1.2"))
 	api(platform("org.jetbrains.kotlinx:kotlinx-coroutines-bom:1.10.2"))
 	api(platform("org.jetbrains.kotlinx:kotlinx-serialization-bom:1.9.0"))

spring-webflux/src/test/java/org/springframework/web/reactive/result/method/annotation/MultipartWebClientIntegrationTests.java

@@ -25,7 +25,6 @@ import java.util.stream.Collectors;
 
 import com.fasterxml.jackson.annotation.JsonCreator;
 import com.fasterxml.jackson.annotation.JsonProperty;
-import org.junit.jupiter.api.condition.JRE;
 import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
 import reactor.core.scheduler.Schedulers;
@@ -61,10 +60,8 @@ import org.springframework.web.reactive.function.client.WebClient;
 import org.springframework.web.server.adapter.WebHttpHandlerBuilder;
 import org.springframework.web.testfixture.http.server.reactive.bootstrap.AbstractHttpHandlerIntegrationTests;
 import org.springframework.web.testfixture.http.server.reactive.bootstrap.HttpServer;
-import org.springframework.web.testfixture.http.server.reactive.bootstrap.JettyHttpServer;
 
 import static org.assertj.core.api.Assertions.assertThat;
-import static org.assertj.core.api.Assumptions.assumeThat;
 
 class MultipartWebClientIntegrationTests extends AbstractHttpHandlerIntegrationTests {
 
@@ -169,11 +166,6 @@ class MultipartWebClientIntegrationTests extends AbstractHttpHandlerIntegrationT
 
 	@ParameterizedHttpServerTest
 	void transferTo(HttpServer httpServer) throws Exception {
-		// TODO https://github.com/spring-projects/spring-framework/issues/35531
-		if (JRE.JAVA_25.isCurrentVersion()) {
-			assumeThat(httpServer).isNotInstanceOf(JettyHttpServer.class);
-		}
-
 		startServer(httpServer);
 
 		Flux<String> result = webClient