Bump docker/build-push-action from 3 to 6

Bumps [docker/build-push-action](/~https://github.com/docker/build-push-action) from 3 to 6.
- [Release notes](/~https://github.com/docker/build-push-action/releases)
- [Commits](docker/build-push-action@v3...v6)

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

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

.github/workflows/build.js.yml

@@ -20,7 +20,7 @@ jobs:
         uses: docker/setup-buildx-action@v2
 
       - name: Build backend image
-        uses: docker/build-push-action@v3
+        uses: docker/build-push-action@v6
         with:
           context: backend
           file: backend/Dockerfile
@@ -48,7 +48,7 @@ jobs:
         uses: docker/setup-buildx-action@v2
 
       - name: Build frontend image
-        uses: docker/build-push-action@v3
+        uses: docker/build-push-action@v6
         with:
           context: frontend
           file: frontend/Dockerfile
@@ -76,7 +76,7 @@ jobs:
         uses: docker/setup-buildx-action@v2
 
       - name: Build modelscan image
-        uses: docker/build-push-action@v3
+        uses: docker/build-push-action@v6
         with:
           context: lib/modelscan_api
           file: lib/modelscan_api/Dockerfile