Fix attestation subject name?

Author: sourcefrog

.github/workflows/container.yml

@@ -40,7 +40,7 @@ jobs:
         id: meta
         uses: docker/metadata-action@v5
         with:
-          images: ${{ env.REGISTRY }}/${{ github.repository_owner }}/${{ github.repository }}
+          images: ${{ env.REGISTRY }}/${{ github.repository }}
 
       - name: Build and push container image
         id: push
@@ -56,6 +56,6 @@ jobs:
       - name: Generate artifact attestation
         uses: actions/attest-build-provenance@v2
         with:
-          subject-name: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME}}
+          subject-name: ${{ env.REGISTRY }}/${{ github.repository }}
           subject-digest: ${{ steps.push.outputs.digest }}
           push-to-registry: true