INT-4018: Resolve some TODOs

JIRA: https://jira.spring.io/browse/INT-4018

* Resolve some TODOs as expected
* Remove some as logically or physically with useless effort
* Leave others for future considerations

spring-integration-websocket/src/test/java/org/springframework/integration/websocket/client/StompIntegrationTests.java

@@ -487,7 +487,7 @@ public class StompIntegrationTests extends LogAdjustingTestSupport {
 			configurer.enableSimpleBroker("/topic", "/queue");
 		}
 
-		//TODO SimpleBrokerMessageHandler doesn't support RECEIPT frame, hence we emulate it this way
+		//SimpleBrokerMessageHandler doesn't support RECEIPT frame, hence we emulate it this way
 		@Bean
 		public ApplicationListener<SessionSubscribeEvent> webSocketEventListener(
 				final AbstractSubscribableChannel clientOutboundChannel) {