Bump actions/checkout from 4 to 6

Bumps [actions/checkout](https://github.com/actions/checkout) from 4 to 6.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v4...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>

Author: dependabot[bot]

.github/workflows/test.yml

@@ -27,7 +27,7 @@ jobs:
             version: 20
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - name: configure
         run: cmake -S. -Bbuild
       - name: build-${{ matrix.os.name }}
@@ -45,7 +45,7 @@ jobs:
     environment:
       name: MyEnvironment
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - uses: actions/download-artifact@v4
       - uses: ./
         with: