Align Actuator sample's tests with endpoint contextId changes

See gh-10980

spring-boot-samples/spring-boot-sample-actuator/src/test/java/sample/actuator/SampleActuatorApplicationTests.java

@@ -219,8 +219,9 @@ public class SampleActuatorApplicationTests {
 				.withBasicAuth("user", getPassword())
 				.getForEntity("/application/beans", Map.class);
 		assertThat(entity.getStatusCode()).isEqualTo(HttpStatus.OK);
-		assertThat(entity.getBody()).containsOnlyKeys("beans", "parent", "id");
-		assertThat(((String) entity.getBody().get("id"))).startsWith("application");
+		assertThat(entity.getBody()).containsOnlyKeys("beans", "parent", "contextId");
+		assertThat(((String) entity.getBody().get("contextId")))
+				.startsWith("application");
 	}
 
 	@SuppressWarnings("unchecked")