Update actions/checkout action to v6 (#433)

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

Author: renovate[bot]

.github/workflows/bump.yaml

@@ -11,7 +11,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout code changes
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Update dependencies
         uses: wader/bump/action@master

.github/workflows/docker-image.yml

@@ -13,7 +13,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout code changes
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Prepare Docker
         uses: docker/setup-buildx-action@v3

.github/workflows/unit-test.yml

@@ -21,7 +21,7 @@ jobs:
         os: [ ubuntu-latest, windows-latest, macos-13 ] # pin macos to latest x64 image
     steps:
       - name: Checkout code changes
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Setup FFmpeg
         uses: FedericoCarboni/setup-ffmpeg@v3
@@ -66,7 +66,7 @@ jobs:
       security-events: write
     steps:
       - name: Checkout code changes
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
         with:
           ref: ${{ github.event.pull_request.head.sha || github.sha }}
           fetch-depth: 0