collab: Remove `POST /billing/subscriptions` endpoint (#34928)

This PR removes the `POST /billing/subscriptions` endpoint, as it has
been moved to `cloud.zed.dev`.

Release Notes:

- N/A
056003860aMarshall Bowers committed on 7/22/2025, 10:57:07 PM· committed by GitHubparent5d985fa
3 files changedLine totals unavailable