Add missing dependency and remove warnings

See gh-22171

framework-docs/src/main/kotlin/org/springframework/docs/web/websocket/stomp/websocketstompdestinationseparator/RedController.kt

@@ -14,6 +14,7 @@
  * limitations under the License.
  */
 
+@file:Suppress("UNUSED_PARAMETER")
 package org.springframework.docs.web.websocket.stomp.websocketstompdestinationseparator
 
 import org.springframework.messaging.handler.annotation.DestinationVariable
@@ -26,7 +27,7 @@ import org.springframework.stereotype.Controller
 class RedController {
 
 	@MessageMapping("blue.{green}")
-	fun handleGreen(@DestinationVariable green: String?) {
+	fun handleGreen(@DestinationVariable green: String) {
 		// ...
 	}
 }

framework-docs/src/main/kotlin/org/springframework/docs/web/websocket/stomp/websocketstomphandlebrokerrelayconfigure/WebSocketConfiguration.kt

@@ -14,6 +14,7 @@
  * limitations under the License.
  */
 
+@file:Suppress("DEPRECATION")
 package org.springframework.docs.web.websocket.stomp.websocketstomphandlebrokerrelayconfigure
 
 import org.springframework.context.annotation.Configuration

framework-docs/src/main/kotlin/org/springframework/docs/web/websocket/stomp/websocketstompinterceptors/MyChannelInterceptor.kt

@@ -14,6 +14,7 @@
  * limitations under the License.
  */
 
+@file:Suppress("UNUSED_VARIABLE")
 package org.springframework.docs.web.websocket.stomp.websocketstompinterceptors
 
 import org.springframework.messaging.Message

framework-docs/src/main/kotlin/org/springframework/docs/web/websocket/stomp/websocketstompserverconfig/JettyWebSocketConfiguration.kt

@@ -24,7 +24,6 @@ import org.springframework.web.socket.config.annotation.WebSocketMessageBrokerCo
 import org.springframework.web.socket.server.jetty.JettyRequestUpgradeStrategy
 import org.springframework.web.socket.server.support.DefaultHandshakeHandler
 import java.time.Duration
-import java.util.function.Consumer
 
 // tag::snippet[]
 @Configuration