🔧 Replace toList() with collect(Collectors.toList()) (#3259)

# Description of Changes

Please provide a summary of the changes, including:

- Replaced the usage of `toList()` with `collect(Collectors.toList())`
in `DatabaseService.java`.

---

## Checklist

### General

- [x] I have read the [Contribution
Guidelines](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/CONTRIBUTING.md)
- [x] I have read the [Stirling-PDF Developer
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/DeveloperGuide.md)
(if applicable)
- [ ] I have read the [How to add new languages to
Stirling-PDF](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/HowToAddNewLanguage.md)
(if applicable)
- [x] I have performed a self-review of my own code
- [x] My changes generate no new warnings

### Documentation

- [ ] I have updated relevant docs on [Stirling-PDF's doc
repo](https://github.com/Stirling-Tools/Stirling-Tools.github.io/blob/main/docs/)
(if functionality has heavily changed)
- [ ] I have read the section [Add New Translation
Tags](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/HowToAddNewLanguage.md#add-new-translation-tags)
(for new translation tags only)

### UI Changes (if applicable)

- [ ] Screenshots or videos demonstrating the UI changes are attached
(e.g., as comments or direct attachments in the PR)

### Testing (if applicable)

- [ ] I have tested my changes locally. Refer to the [Testing
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/DeveloperGuide.md#6-testing)
for more details.

src/main/java/stirling/software/SPDF/config/security/database/DatabaseService.java

@@ -17,6 +17,7 @@ import java.time.format.DateTimeFormatter;
 import java.util.ArrayList;
 import java.util.Comparator;
 import java.util.List;
+import java.util.stream.Collectors;
 
 import javax.sql.DataSource;
 
@@ -169,7 +170,7 @@ public class DatabaseService implements DatabaseInterface {
         List<FileInfo> filteredBackupList =
                 this.getBackupList().stream()
                         .filter(backup -> !backup.getFileName().startsWith(BACKUP_PREFIX + "user_"))
-                        .toList();
+                        .collect(Collectors.toList());
 
         if (filteredBackupList.size() > 5) {
             deleteOldestBackup(filteredBackupList);