Bump actions/checkout from 5 to 6 (#13)

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
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

.github/workflows/master.yml

@@ -25,7 +25,7 @@ jobs:
             index: 'ON'
     steps:
       - name: Clone
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
         with:
           submodules: recursive
       - name: Update
@@ -92,7 +92,7 @@ jobs:
           token: ${{ secrets.ALL }}
           environment: github-pages
       - name: Clone
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - name: Setup
         uses: actions/setup-python@v6
         with: