Use a random port in tests

listen() is on 80 while listen(0) is random.

vertx-mutiny-clients/vertx-mutiny-core/src/test/java/io/smallrye/mutiny/vertx/core/ExpectationsTest.java

@@ -53,7 +53,7 @@ public void httpAssertion() {
                             .setStatusCode(200)
                             .putHeader("content-type", "text/plain")
                             .endAndForget("Yolo"))
-                    .listen()
+                    .listen(0)
                     .await().atMost(Duration.ofSeconds(30));
 
             int port = server.actualPort();