ci: bump actions/checkout from 5 to 6 (#451)

Bumps [actions/checkout](https://github.com/actions/checkout) from 5 to 6.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v5...v6)

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

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

Author: dependabot[bot]

.github/workflows/check.yml

@@ -4,7 +4,7 @@ jobs:
   check:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: actions/setup-python@v6
       - name: install tools
         run: pip install flake8 black

.github/workflows/deploy.yml

@@ -9,7 +9,7 @@ jobs:
   deploy:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - name: Upload website to interop.seemann.io
         uses: burnett01/rsync-deployments@33214bd98ba4ac2be90f5976672b3f030fce9ce4 # v7.1.0
         with:

.github/workflows/interop.yml

@@ -27,7 +27,7 @@ jobs:
           STARTTIME=$(date +%s)
           echo $STARTTIME
           echo "starttime=$STARTTIME" >> $GITHUB_OUTPUT
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: actions/setup-python@v6
         with:
           python-version: 3.8
@@ -55,7 +55,7 @@ jobs:
       matrix:
         image: [ 'quic-network-simulator', 'quic-interop-iperf-endpoint' ]
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
     - name: Pull
       run: |
         URL="martenseemann/${{ matrix.image }}"
@@ -81,7 +81,7 @@ jobs:
         image: ${{ fromJson(needs.config.outputs.images) }}
     name: Pull ${{ matrix.image }}
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - name: Run docker pull
         run: |
           URL=$(jq -r '.["${{ matrix.image }}"].image' implementations.json)
@@ -112,7 +112,7 @@ jobs:
         client: ${{ fromJson(needs.config.outputs.clients) }}
     name: (${{ matrix.server }} - ${{ matrix.client }})
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       # Remove this when GitHub runner gets docker engine >= v28.1.0.
       - uses: docker/setup-docker-action@v4
         with:
@@ -198,7 +198,7 @@ jobs:
     env:
       LOGNAME: ${{ needs.config.outputs.logname }}
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: actions/setup-python@v6
         with:
           python-version: 3.8