Adopt to newly introduced ParameterAccessor.getScrollPosition().

Closes #2494

src/test/java/org/springframework/data/elasticsearch/repository/query/StubParameterAccessor.java

@@ -20,6 +20,7 @@ import java.util.Iterator;
 import java.util.Optional;
 
 import org.springframework.data.domain.Pageable;
+import org.springframework.data.domain.ScrollPosition;
 import org.springframework.data.domain.Sort;
 import org.springframework.data.repository.query.ParameterAccessor;
 
@@ -37,6 +38,11 @@ class StubParameterAccessor implements ElasticsearchParameterAccessor {
 		this.values = values;
 	}
 
+	@Override
+	public ScrollPosition getScrollPosition() {
+		return null;
+	}
+
 	/*
 	 * (non-Javadoc)
 	 * @see org.springframework.data.repository.query.ParameterAccessor#getPageable()