Bump actions/checkout from 5 to 6 in /.github/workflows

Bumps [actions/checkout](https://github.com/actions/checkout) from 5 to 6.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v5...v6)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Author: Blackjacx

frameworks/gh-actions/spm-only-test.yml

@@ -17,7 +17,7 @@ jobs:
       - uses: swift-actions/setup-swift@v3
         with:
           swift-version: ${{ matrix.swift }}
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - name: Log Swift Version
         run: swift --version
       - name: Log Xcode Versions