Bump actions/checkout from 4 to 5 in the ci-dependencies group

Bumps the ci-dependencies group with 1 update: [actions/checkout](https://github.com/actions/checkout).


Updates `actions/checkout` from 4 to 5
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](https://github.com/actions/checkout/compare/v4...v5)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '5'
  dependency-type: direct:production
  update-type: version-update:semver-major
  dependency-group: ci-dependencies
...

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/dart.yml

@@ -14,7 +14,7 @@ jobs:
         os: [ubuntu-latest]
         sdk: [stable]
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - uses: dart-lang/setup-dart@v1.4
         with:
           sdk: ${{ matrix.sdk }}