ci: bump actions/checkout from 4 to 7

Bumps [actions/checkout](https://github.com/actions/checkout) from 4 to 7.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v4...v7)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '7'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

.github/workflows/ci.yml

@@ -25,7 +25,7 @@ jobs:
         # declared minimum SDK (pubspec `environment: sdk`).
         sdk: [stable, "3.5.0"]
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v7
       - uses: dart-lang/setup-dart@v1
         with:
           sdk: ${{ matrix.sdk }}
@@ -49,7 +49,7 @@ jobs:
     name: pub.dev score (pana)
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v7
       - uses: dart-lang/setup-dart@v1
       - name: Install dependencies
         run: dart pub get