Harmonize Kotlin example for HTTP Service client support

See gh-48577

Signed-off-by: jwalter <[email protected]>

Author: jwalter

documentation/spring-boot-docs/src/main/kotlin/org/springframework/boot/docs/io/restclient/httpservice/groups/EchoService.kt

@@ -19,7 +19,6 @@ import org.springframework.web.bind.annotation.RequestBody
 import org.springframework.web.service.annotation.HttpExchange
 import org.springframework.web.service.annotation.PostExchange
 
-@HttpExchange("echo")
 interface EchoService {
 
 	@PostExchange