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/ci.yaml

@@ -61,7 +61,7 @@ jobs:
         password: ${{ secrets.DOCKERHUB_TOKEN }}
     - id: vars
       run: echo "tag=$(make tag)" >> $GITHUB_OUTPUT
-    - uses: docker/build-push-action@v5
+    - uses: docker/build-push-action@v6
       with:
         context: .
         push: true