[FIX] correct indent for labels list

Author: alpae

.github/workflows/docker-image.yml

@@ -37,7 +37,7 @@ jobs:
             type=semver,pattern={{major}}.{{minor}}
             type=semver,pattern={{major}}
             type=sha
-        labels: |
+          labels: |
             org.opencontainers.image.source=${{ github.repository }}
             org.opencontainers.image.revision=${{ github.sha }}