Bump docker/build-push-action from 2.4.0 to 4.0.0

Bumps [docker/build-push-action](https://github.com/docker/build-push-action) from 2.4.0 to 4.0.0.
- [Release notes](https://github.com/docker/build-push-action/releases)
- [Commits](https://github.com/docker/build-push-action/compare/v2.4.0...v4.0.0)

---
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.yml

@@ -43,7 +43,7 @@ jobs:
           esac;
 
       - name: build & push image
-        uses: docker/build-push-action@v2.4.0
+        uses: docker/build-push-action@v4.0.0
         with:
           context: .
           file: docker/alpine/Dockerfile