chore(config): refine testing directory glob patterns in .files.yaml (#4600)

# Description of Changes

- Updated `.github/config/.files.yaml` to refine glob patterns for the
`testing` directory.
- Replaced broad pattern `testing/**` with a more selective pattern
`'testing/**/!(requirements*.txt|requirements*.in)*'` to exclude Python
dependency files.
- Removed redundant `testing/**` entry from the `project` section for
cleaner configuration.

This change ensures that only relevant test files are matched in the
project configuration while excluding requirements files from triggering
workflow changes.

---

## 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/devGuide/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/devGuide/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/devGuide/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/devGuide/DeveloperGuide.md#6-testing)
for more details.

---------

Co-authored-by: Reece Browne <74901996+reecebrowne@users.noreply.github.com>

.github/config/.files.yaml

@@ -17,7 +17,7 @@ project: &project
   - exampleYmlFiles/**
   - gradle/**
   - libs/**
-  - testing/**
+  - 'testing/**/!(requirements*.txt|requirements*.in)*'
   - build.gradle
   - Dockerfile
   - Dockerfile.fat
@@ -29,7 +29,6 @@ project: &project
   - settings.gradle
   - frontend/**
   - docker/**
-  - testing/**
 
 frontend: &frontend
   - frontend/**