Polish "Harmonize Kotlin example for HTTP Service client support"

See gh-48577

Author: snicoll

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

@@ -0,0 +1,14 @@
+package org.springframework.boot.docs.io.restclient.httpservice.groups
+
+import org.springframework.boot.autoconfigure.SpringBootApplication
+import org.springframework.boot.runApplication
+import org.springframework.web.service.registry.ImportHttpServices
+
+@SpringBootApplication
+@ImportHttpServices(group = "echo", basePackages = ["com.example.myclients"])
+class MyApplication
+
+fun main(args: Array<String>) {
+	runApplication<MyApplication>(*args)
+}
+