Fix workflow macos-11 to macos-latest (microsoft#7006)

# Pull Request

## 📖 Description

Fix workflow macos-11 to macos-latest, macos-11 has been [deprecated](https://github.blog/changelog/2024-05-20-actions-upcoming-changes-to-github-hosted-macos-runners/) and therefore will never run.

## ✅ Checklist

### General

<!--- Review the list and put an x in the boxes that apply. -->

- [ ] I have included a change request file using `$ npm run change`
- [ ] I have added tests for my changes.
- [ ] I have tested my changes.
- [ ] I have updated the project documentation to reflect my changes.
- [x] I have read the [CONTRIBUTING](https://github.com/microsoft/fast/blob/master/CONTRIBUTING.md) documentation and followed the [standards](https://github.com/microsoft/fast/blob/master/CODE_OF_CONDUCT.md#our-standards) for this project.

.github/workflows/ci-validate-platforms.yml

@@ -19,7 +19,7 @@ jobs:
     strategy:
       fail-fast: true
       matrix:
-        os: [ubuntu-latest, windows-latest, macos-11]
+        os: [ubuntu-latest, windows-latest, macos-latest]
 
     env:
       PLAYWRIGHT_BROWSERS_PATH: 0