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](docker/build-push-action@v5...v6)

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

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

.github/workflows/publish.yml

@@ -72,7 +72,7 @@ jobs:
         run: ruby -e 'puts "version=#{RUBY_VERSION}"' >> $GITHUB_OUTPUT
         if: ${{ matrix.entry.build_ruby != '' }}
 
-      - uses: docker/build-push-action@v5
+      - uses: docker/build-push-action@v6
         with:
           build-args: |
             version=${{ matrix.entry.os }}