Bump docker/build-push-action from 5 to 6 (#1686)

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>
Co-authored-by: Michael Müller <[email protected]>

.github/workflows/release-image.yml

@@ -28,7 +28,7 @@ jobs:
 
       - name: Build and push Docker image from master
         if: ${{ github.event_name == 'push' }}
-        uses: docker/build-push-action@v5
+        uses: docker/build-push-action@v6
         with:
           context: .
           file: ./build-image/Dockerfile
@@ -50,7 +50,7 @@ jobs:
 
       - name: Build and push Docker image from release
         if: ${{ github.event_name == 'release' }}
-        uses: docker/build-push-action@v5
+        uses: docker/build-push-action@v6
         with:
           context: .
           file: ./build-image/Dockerfile