chore(deps): bump docker/metadata-action from 5.5.1 to 5.6.1

Bumps [docker/metadata-action](https://github.com/docker/metadata-action) from 5.5.1 to 5.6.1.
- [Release notes](https://github.com/docker/metadata-action/releases)
- [Commits](docker/metadata-action@v5.5.1...v5.6.1)

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

Signed-off-by: dependabot[bot] <[email protected]>

.github/workflows/ci.yml

@@ -108,7 +108,7 @@ jobs:
           password: ${{ secrets.GITHUB_TOKEN }}
       - name: Docker meta
         id: docker_meta
-        uses: docker/metadata-action@v5.5.1
+        uses: docker/metadata-action@v5.6.1
         with:
           images: ghcr.io/c2corg/v6_api
       - name: Checkout repository
@@ -141,7 +141,7 @@ jobs:
           password: ${{ secrets.GITHUB_TOKEN }}
       - name: Docker meta
         id: docker_meta
-        uses: docker/metadata-action@v5.5.1
+        uses: docker/metadata-action@v5.6.1
         with:
           images: ghcr.io/c2corg/v6_api
           flavor: |