Stop referring to obsolete ListenableFuture in documentation

ListenableFuture as deprecated for removal in 6.0 and removed in 7.0.

See gh-33808
See gh-33809
See commit cb8ed43be1
Closes gh-36313

spring-messaging/src/main/java/org/springframework/messaging/tcp/reactor/ReactorNettyTcpClient.java

@@ -208,7 +208,7 @@ public class ReactorNettyTcpClient<P> implements TcpOperations<P> {
 			return handleShuttingDownConnectFailure(handler);
 		}
 
-		// Report first connect to the ListenableFuture
+		// Report first connect to the CompletableFuture
 		CompletableFuture<@Nullable Void> connectFuture = new CompletableFuture<>();
 
 		extendTcpClient(this.tcpClient, handler)

spring-webmvc/src/main/java/org/springframework/web/servlet/mvc/method/annotation/ServletInvocableHandlerMethod.java

@@ -197,7 +197,7 @@ public class ServletInvocableHandlerMethod extends InvocableHandlerMethod {
 	 * Create a nested ServletInvocableHandlerMethod subclass that returns the
 	 * given value (or raises an Exception if the value is one) rather than
 	 * actually invoking the controller method. This is useful when processing
-	 * async return values (for example, Callable, DeferredResult, ListenableFuture).
+	 * async return values (for example, Callable, DeferredResult, CompletableFuture).
 	 */
 	ServletInvocableHandlerMethod wrapConcurrentResult(@Nullable Object result) {
 		return new ConcurrentResultHandlerMethod(result, new ConcurrentResultMethodParameter(result));

spring-websocket/src/main/java/org/springframework/web/socket/messaging/WebSocketStompClient.java

@@ -247,7 +247,7 @@ public class WebSocketStompClient extends StompClientSupport implements SmartLif
 	 * @param handshakeHeaders the headers for the WebSocket handshake
 	 * @param handler the session handler
 	 * @param uriVariables the URI variables to expand into the URL
-	 * @return a {@code ListenableFuture} for access to the session when ready for use
+	 * @return a {@code CompletableFuture} for access to the session when ready for use
 	 * @since 6.0
 	 */
 	public CompletableFuture<StompSession> connectAsync(String url, @Nullable WebSocketHttpHeaders handshakeHeaders,