Align OffsetScrolling to zero-based indexes.

Closes #1764

Author: mp911de

spring-data-r2dbc/src/test/java/org/springframework/data/r2dbc/repository/support/AbstractSimpleR2dbcRepositoryIntegrationTests.java

@@ -857,7 +857,7 @@ void findByScrollPosition() {
 
 		repository
 				.findBy(Example.of(probe, matching().withIgnorePaths("id")),
-						q -> q.sortBy(Sort.by("name")).limit(2).scroll(ScrollPosition.offset(2))) //
+						q -> q.sortBy(Sort.by("name")).limit(2).scroll(ScrollPosition.offset(1))) //
 				.as(StepVerifier::create) //
 				.consumeNextWith(window -> {