gha: fix outputs spelling

Author: haarg

.github/workflows/update-snapshot.yml

@@ -17,7 +17,7 @@ jobs:
           private-key: ${{ secrets.APP_PRIVATE_KEY }}
       - uses: haarg/setup-git-user@v1
         with:
-          app: ${{ steps.app-token.output.app-slug }}
+          app: ${{ steps.app-token.outputs.app-slug }}
       - uses: actions/checkout@v4
         with:
           token: ${{ steps.app-token.outputs.token }}