Bump docker/metadata-action from 5 to 6 (#407)

Bumps [docker/metadata-action](https://github.com/docker/metadata-action) from 5 to 6.
- [Release notes](https://github.com/docker/metadata-action/releases)
- [Commits](docker/metadata-action@v5...v6)

---
updated-dependencies:
- dependency-name: docker/metadata-action
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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Author: dependabot[bot]

.github/workflows/publish-docker.yml

@@ -37,7 +37,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v6
-      - uses: docker/metadata-action@v5
+      - uses: docker/metadata-action@v6
         id: meta
         with:
           images: |