fix: debug stage in container workflow

.github/workflows/build.yaml

@@ -40,8 +40,7 @@ jobs:
       - name: Show tags
         run: |
           echo "Tags generated by metadata-action:\n"
-          tags = "${{ steps.metadata.output.tags }}"
-          for tag in ${{ tags }}; do
+          for tag in ${{ steps.metadata.output.tags }}; do
             echo $tag
           done