docs: updated 'conceptual preview' title (#50326)

asheerrizvi · AndrewKushnir · commit 97285432e37c · 2023-05-16T09:27:56.000-07:00
PR Close #50326
diff --git a/aio/content/tutorial/first-app/first-app-lesson-09.md b/aio/content/tutorial/first-app/first-app-lesson-09.md
@@ -22,7 +22,7 @@ If you have any trouble during this lesson, you can review the completed code fo
    At the end of this lesson, the service reads data from local, static data.
    In a later lesson, you update the service to get data from a web service.
 
-## Conceptual preview of interfaces
+## Conceptual preview of services
 
 This tutorial introduces Angular services and dependency injection.
 
