Bump actions/checkout from 5.0.1 to 6.0.0

Bumps [actions/checkout](https://github.com/actions/checkout) from 5.0.1 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@93cb6ef...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]>

Author: dependabot[bot]

.github/workflows/flutter-ci.yml

@@ -26,7 +26,7 @@ jobs:
         flutter_version: [stable, beta, main]
         os: [ubuntu-latest, macos-latest, windows-latest]
     steps:
-      - uses: actions/checkout@93cb6efe18208431cddfb8368fd83d5badbf9bfd
+      - uses: actions/checkout@1af3b93b6815bc44a9784bd300feb67ff0d1eeb3
       - uses: actions/setup-java@dded0888837ed1f317902acf8a20df0ad188d165
         with:
           distribution: "zulu" # See https://github.com/actions/setup-java#supported-distributions