Bump docker/build-push-action from 5 to 6

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]>

.github/workflows/build.yml

@@ -103,7 +103,7 @@ jobs:
             type=sha
 
       - name: Docker build+push [test]
-        uses: docker/build-push-action@v5
+        uses: docker/build-push-action@v6
         with:
           context: .
           file: ./Dockerfile.build
@@ -133,7 +133,7 @@ jobs:
             type=semver,pattern={{version}}
 
       - name: Docker build+push [private]
-        uses: docker/build-push-action@v5
+        uses: docker/build-push-action@v6
         if: github.event_name == 'push' && env.PRIVATE_REGISTRY_URL != '' && steps.meta-private.outputs.tags != ''
         with:
           context: .
@@ -166,7 +166,7 @@ jobs:
             type=semver,pattern={{major}},enable=${{ !startsWith(github.ref, 'refs/tags/v0.') }}
 
       - name: Docker build+push [public]
-        uses: docker/build-push-action@v5
+        uses: docker/build-push-action@v6
         if: github.event_name == 'push' && env.DOCKER_HUB_USERNAME != '' && steps.meta-public.outputs.tags != ''
         with:
           context: .