build(deps): bump docker/build-push-action from 6.13.0 to 6.15.0 (exercism#207)

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/docker-build-push-image.yml

@@ -97,7 +97,7 @@ jobs:
 
       - name: Build Docker image
         if: ${{steps.dockerfile-exists.outputs.result == 'true' && (inputs.docker_hub || inputs.aws_ecr)}}
-        uses: docker/build-push-action@ca877d9245402d1537745e0e356eab47c3520991
+        uses: docker/build-push-action@471d1dc4e07e5cdedd4c2171150001c434f0b7a4
         with:
           context: .
           file: ./Dockerfile
@@ -109,7 +109,7 @@ jobs:
           platforms: ${{ inputs.platform }}
 
       - name: Push to Docker Hub
-        uses: docker/build-push-action@ca877d9245402d1537745e0e356eab47c3520991
+        uses: docker/build-push-action@471d1dc4e07e5cdedd4c2171150001c434f0b7a4
         if: ${{steps.dockerfile-exists.outputs.result == 'true' && inputs.docker_hub}}
         with:
           context: .
@@ -125,7 +125,7 @@ jobs:
           platforms: ${{ inputs.platform }}
 
       - name: Push to AWS ECR
-        uses: docker/build-push-action@ca877d9245402d1537745e0e356eab47c3520991
+        uses: docker/build-push-action@471d1dc4e07e5cdedd4c2171150001c434f0b7a4
         if: ${{steps.dockerfile-exists.outputs.result == 'true' && inputs.aws_ecr}}
         with:
           context: .