Disable flaky unit test for undertow

spring-webflux/src/test/java/org/springframework/web/reactive/function/MultipartRouterFunctionIntegrationTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2022 the original author or authors.
+ * Copyright 2002-2023 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.
@@ -163,6 +163,8 @@ class MultipartRouterFunctionIntegrationTests extends AbstractRouterFunctionInte
 
 	@ParameterizedHttpServerTest
 	void proxy(HttpServer httpServer) throws Exception {
+		assumeFalse(httpServer instanceof UndertowHttpServer, "Undertow currently fails proxying requests");
+
 		startServer(httpServer);
 
 		Mono<ResponseEntity<Void>> result = webClient