Bump docker/build-push-action from 5 to 6 (#29)

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]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

.github/workflows/build.yml

@@ -36,7 +36,7 @@ jobs:
         with:
           images: ghcr.io/EspressoSystems/nix
 
-      - uses: docker/build-push-action@v5
+      - uses: docker/build-push-action@v6
         name: Build and Push Docker
         with:
           context: .