ci: add cleanup step to remove temporary files in workflow (#3782)

# Description of Changes

# Description of Changes

- Added a new step `Cleanup temporary files` at the end of the
`check_properties.yml` GitHub Actions workflow.
- This step ensures temporary files such as `pr-branch`, `.properties`
comparison files, and result artifacts are deleted after the job.
- The `continue-on-error: true` flag guarantees cleanup runs even if
previous steps fail.

This change helps prevent workspace clutter and reduces disk usage in CI
runs.

---

## 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.

.github/workflows/check_properties.yml

@@ -269,3 +269,12 @@ jobs:
         run: |
           echo "Failing the job because errors were detected."
           exit 1
+
+      - name: Cleanup temporary files
+        if: always()
+        run: |
+          echo "Cleaning up temporary files..."
+          rm -rf pr-branch
+          rm -f pr-branch-messages_en_GB.properties main-branch-messages_en_GB.properties changed_files.txt result.txt
+          echo "Cleanup complete."
+        continue-on-error: true # Ensure cleanup runs even if previous steps fail