Fix variable reference syntax in sync-upstream.yml

Author: Zarloc

.github/workflows/sync-upstream.yml

@@ -36,7 +36,7 @@ jobs:
           sed -i 's/return ((user & endpoint) == endpoint);/return true;/' src/web/api/http_auth.h
           
           # 4. Add this file
-          echo "${vars.SYNC_UPSTREAM}" > .github/workflows/sync-upstream.yml
+          echo "$vars.SYNC_UPSTREAM" > .github/workflows/sync-upstream.yml
 
           # 5. Commit the changes
           git add src/web/api/http_auth.h