Remove outdated note

See gh-20606

spring-test/src/main/java/org/springframework/test/web/reactive/server/WebTestClient.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2023 the original author or authors.
+ * Copyright 2002-2024 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.
@@ -77,14 +77,6 @@
  * <li>...
  * </ul>
  *
- * <p><strong>Warning</strong>: {@code WebTestClient} is not usable yet in
- * Kotlin due to a <a href="https://youtrack.jetbrains.com/issue/KT-5464">type inference issue</a>
- * which is expected to be fixed as of Kotlin 1.3. You can watch
- * <a href="https://github.com/spring-projects/spring-framework/issues/20606">gh-20606</a>
- * for up-to-date information. Meanwhile, the proposed alternative is to use
- * directly {@link WebClient} with its Reactor and Spring Kotlin extensions to
- * perform integration tests on an embedded WebFlux server.
- *
  * @author Rossen Stoyanchev
  * @author Brian Clozel
  * @author Sam Brannen