fix(cloudflare): Use original waitUntil to not create a deadlock (#21197)

follow up to: #21156

This prevents a deadlock in the `waitUntil`, which happened in the
sentry-mcp:

<img width="972" height="119" alt="Screenshot 2026-05-27 at 17 04 19"
src="https://github.com/user-attachments/assets/18ec0f64-c766-4f6f-82a6-9453280668a5"
/>