Bump docker/build-push-action from 5 to 6 (#10)

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
...

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Author: dependabot[bot]

.github/workflows/build.yml

@@ -83,7 +83,7 @@ jobs:
       # https://github.com/docker/build-push-action
       - name: Build and push Docker image
         if: ${{ env.NGINX_VERSION != '' }}
-        uses: docker/build-push-action@v5
+        uses: docker/build-push-action@v6
         with:
           context: .
           push: ${{ github.event_name != 'pull_request' }}