ci(gha): specify the registry as ghcr.io

.github/workflows/ci.yml

@@ -33,7 +33,7 @@ jobs:
       - name: Log in to the Container registry
         uses: docker/login-action@f054a8b539a109f9f41c372932f1ae047eff08c9
         with:
-          registry: ${{ env.REGISTRY }}
+          registry: ghcr.io
           username: ${{ github.actor }}
           password: ${{ secrets.GITHUB_TOKEN }}