Bump docker/build-push-action from 6.13.0 to 6.15.0 (#8271)

Author: dependabot[bot]

.github/workflows/docker-publish.yaml

@@ -22,7 +22,7 @@ jobs:
           username: weaveworkseksctlci
           password: ${{ secrets.DOCKER_HUB_PASSWORD }}
       - name: Build and push Docker image
-        uses: docker/build-push-action@ca877d9245402d1537745e0e356eab47c3520991 #6.13.0
+        uses: docker/build-push-action@471d1dc4e07e5cdedd4c2171150001c434f0b7a4 #6.15.0
         with:
           context: .
           push: true

.github/workflows/ecr-publish.yaml

@@ -41,7 +41,7 @@ jobs:
           images: ${{ env.REGISTRY }}/${{ env.REGISTRY_ALIAS }}/${{ env.REPOSITORY }}
 
       - name: Build and push container image to ECR
-        uses: docker/build-push-action@ca877d9245402d1537745e0e356eab47c3520991 #6.13.0
+        uses: docker/build-push-action@471d1dc4e07e5cdedd4c2171150001c434f0b7a4 #6.15.0
         with:
           context: .
           push: true