Simplify CLI integration auto-config test by removing use of Artemis

Artemis seems to be a bit flakey which is causing sporadic build
failures, for example due to an NPE in Artemis' code.

spring-boot-cli/test-samples/app.groovy

@@ -0,0 +1,17 @@
+@Configuration
+class App {
+
+	@Bean
+	MyService myService() {
+		return new MyService()
+	}
+
+}
+
+class MyService {
+
+	String sayWorld() {
+		return "World!"
+	}
+
+}