Update actions/checkout action to v6 (#24)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

.github/workflows/analyze.yml

@@ -8,7 +8,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout code
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - name: Setup Flutter
         uses: ./.github/actions/setup
       - name: Analyze

.github/workflows/build.yml

@@ -12,7 +12,7 @@ jobs:
     runs-on: ${{ inputs.platform == 'linux' && 'ubuntu-latest' || inputs.platform == 'windows' && 'windows-latest' || inputs.platform == 'macos' && 'macos-latest' }}
     steps:
       - name: Checkout code
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - name: Install dependencies
         if: ${{ inputs.platform == 'linux' }}
         run: |

.github/workflows/test.yml

@@ -12,7 +12,7 @@ jobs:
     runs-on: ${{ inputs.platform == 'linux' && 'ubuntu-latest' || inputs.platform == 'windows' && 'windows-latest' || inputs.platform == 'macos' && 'macos-latest' }}
     steps:
       - name: Checkout code
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - name: Setup Flutter
         uses: ./.github/actions/setup
       - name: Run Tests