Bump actions/checkout from 4.2.2 to 6.0.0 (#813)

Bumps [actions/checkout](https://github.com/actions/checkout) from 4.2.2 to 6.0.0.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@11bd719...1af3b93)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: 6.0.0
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

.github/workflows/dart.yml

@@ -18,7 +18,7 @@ jobs:
       matrix:
         sdk: [stable, dev]
     steps:
-      - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683
+      - uses: actions/checkout@1af3b93b6815bc44a9784bd300feb67ff0d1eeb3
       - uses: dart-lang/setup-dart@e51d8e571e22473a2ddebf0ef8a2123f0ab2c02c
         with:
           sdk: ${{ matrix.sdk }}
@@ -61,7 +61,7 @@ jobs:
           - os: macos-latest
             platform: chrome
     steps:
-      - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683
+      - uses: actions/checkout@1af3b93b6815bc44a9784bd300feb67ff0d1eeb3
       - uses: dart-lang/setup-dart@e51d8e571e22473a2ddebf0ef8a2123f0ab2c02c
         with:
           sdk: ${{ matrix.sdk }}