chore: Refactor DatasetService to improve search functionality and remove unnecessary print statement

src/main/java/de/uni_passau/fim/PADAS/group3/DataDash/model/DatasetService.java

@@ -93,7 +93,6 @@ public class DatasetService {
 
     public Page<Dataset> searchByOptionalCriteria(String search, Pageable pageable) {
         if (search.equals("%")) {
-            System.out.println("searching for all datasets");
             return datasetRepository.findAll(pageable);
         }
         return datasetRepository.searchByOptionalCriteria(Optional.ofNullable(search), pageable);