ci: fix release image version (#47)

Author: GoshaDo

.github/workflows/release.yaml

@@ -30,7 +30,7 @@ jobs:
           context: .
           platforms: linux/amd64,linux/arm64
           push: true
-          tags: quickube/piper:${{ github.ref_name }},quickube/piper:${{ github.ref_name }}:latest
+          tags: quickube/piper:${{ github.ref_name }},quickube/piper:latest
           labels: ${{ steps.meta.outputs.labels }}
           cache-from: type=gha
           cache-to: type=gha,mode=max