Bump docker/build-push-action from 6.13.0 to 6.15.0 (#254)

Bumps [docker/build-push-action](https://github.com/docker/build-push-action) from 6.13.0 to 6.15.0.
- [Release notes](https://github.com/docker/build-push-action/releases)
- [Commits](docker/build-push-action@ca877d9...471d1dc)

---
updated-dependencies:
- dependency-name: docker/build-push-action
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

.github/workflows/test.yml

@@ -37,7 +37,7 @@ jobs:
           install: true
 
       - name: Build Docker image and store in cache
-        uses: docker/build-push-action@ca877d9245402d1537745e0e356eab47c3520991
+        uses: docker/build-push-action@471d1dc4e07e5cdedd4c2171150001c434f0b7a4
         with:
           context: .
           push: false