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/backend-docker.yml

@@ -43,7 +43,7 @@ jobs:
 
     - name: Build and Push
       id: docker_build
-      uses: docker/build-push-action@v5
+      uses: docker/build-push-action@v6
       with:
         builder: ${{ steps.buildx.outputs.name }}
         context: ./