Use correct ScrollPosition factory methods in reference docs.

Closes #2963

src/main/antora/modules/ROOT/pages/repositories/scrolling.adoc

@@ -90,7 +90,7 @@ interface UserRepository extends Repository<User, Long> {
 }
 
 WindowIterator<User> users = WindowIterator.of(position -> repository.findFirst10ByLastnameOrderByFirstname("Doe", position))
-  .startingAt(KeysetScrollPosition.initial()); <1>
+  .startingAt(ScrollPosition.keyset()); <1>
 ----
 <1> Start at the very beginning and do not apply additional filtering.
 

src/main/asciidoc/repositories-scrolling.adoc

@@ -91,7 +91,7 @@ interface UserRepository extends Repository<User, Long> {
 }
 
 WindowIterator<User> users = WindowIterator.of(position -> repository.findFirst10ByLastnameOrderByFirstname("Doe", position))
-  .startingAt(KeysetScrollPosition.initial()); <1>
+  .startingAt(ScrollPosition.keyset()); <1>
 ----
 <1> Start at the very beginning and do not apply additional filtering.
 ====