ci: bump docker/build-push-action from 6.8.0 to 6.9.0

Bumps [docker/build-push-action](https://github.com/docker/build-push-action) from 6.8.0 to 6.9.0.
- [Release notes](https://github.com/docker/build-push-action/releases)
- [Commits](docker/build-push-action@v6.8.0...v6.9.0)

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

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

.github/workflows/build.yml

@@ -109,7 +109,7 @@ jobs:
             core.setOutput("tags", tags);
 
       - name: Push Docker image
-        uses: docker/build-push-action@v6.8.0
+        uses: docker/build-push-action@v6.9.0
         id: docker_build_and_push
         with:
           context: "${{ env.DOCKER_EXAMPLES_DIRECTORY }}/${{ env.backend_dir_name }}"