ci: bump actions/checkout from 4 to 7

Bumps [actions/checkout](https://github.com/actions/checkout) from 4 to 7.
- [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...v7)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '7'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/docker-publish.yml

@@ -22,7 +22,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v7
 
       - uses: actions/setup-python@v5
         with:
@@ -39,7 +39,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v7
 
       - name: Validate compose example
         run: docker compose --file compose.example.yaml config --quiet
@@ -59,7 +59,7 @@ jobs:
     if: github.event_name == 'push' && startsWith(github.ref, 'refs/tags/')
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v7
 
       # Every tag of a release must resolve to one manifest digest, so the
       # image is built once and all tags are attached to that single build.