ci: bump actions/checkout from 4 to 6 in the actions group (#478)

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


Updates `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](https://github.com/actions/checkout/compare/v4...v6)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
  dependency-group: actions
...

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

.github/workflows/ci.yml

@@ -10,7 +10,7 @@ jobs:
       matrix:
         os: [ubuntu-latest, windows-latest, macos-latest]
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - uses: subosito/flutter-action@v2
         with:
           cache: true

.github/workflows/gh-release.yml

@@ -19,7 +19,7 @@ jobs:
       SECRET: ${{ secrets.SECRET }}
     steps:
       - name: Checkout Frosty repo
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
       
       # Setup Java so that we can build the APK.
       - name: Set up Java

.github/workflows/pr-check.yml

@@ -7,7 +7,7 @@ jobs:
     name: Check and test
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - uses: subosito/flutter-action@v2
         with:
           cache: true

.github/workflows/store-release.yml

@@ -29,7 +29,7 @@ jobs:
 
     steps:
       - name: Checkout Frosty repo
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
 
       # Install Ruby and install/cache dependencies with bundler in order to use fastlane.
       - name: Set up Ruby and Bundler
@@ -82,7 +82,7 @@ jobs:
       MATCH_PASSWORD: ${{ secrets.MATCH_PASSWORD }}
     steps:
       - name: Checkout Frosty repo
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
 
         # Always pick the newest production Xcode on the runner
       - uses: maxim-lobanov/setup-xcode@v1