Bump docker/build-push-action from 5 to 6

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

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

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

.github/workflows/ci.yml

@@ -40,7 +40,7 @@ jobs:
           username: ${{ github.repository_owner }}
           password: ${{ secrets.GITHUB_TOKEN }}
       - name: Build image
-        uses: docker/build-push-action@v5
+        uses: docker/build-push-action@v6
         with:
           tags: |
             ghcr.io/${{ github.repository }}:latest