chore(deps): bump docker/build-push-action from 4 to 6

Bumps [docker/build-push-action](https://github.com/docker/build-push-action) from 4 to 6.
- [Release notes](https://github.com/docker/build-push-action/releases)
- [Commits](docker/build-push-action@v4...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/main.yml

@@ -209,7 +209,7 @@ jobs:
           password: ${{ secrets.FLY_API_TOKEN }}
 
       - name: 🐳 Docker build
-        uses: docker/build-push-action@v4
+        uses: docker/build-push-action@v6
         with:
           context: .
           file: ./packages/newsroom/Dockerfile
@@ -312,7 +312,7 @@ jobs:
           password: ${{ secrets.FLY_API_TOKEN }}
 
       - name: 🐳 Docker build
-        uses: docker/build-push-action@v4
+        uses: docker/build-push-action@v6
         with:
           context: .
           file: ./packages/newspaper/Dockerfile