collab: Remove code for syncing token-based billing events (#30130)

This PR removes the code related to syncing token-based billing events
to Stripe.

We don't need this anymore with the new billing.

Release Notes:

- N/A

crates/collab/src/llm/db/queries.rs

@@ -1,6 +1,5 @@
 use super::*;
 
-pub mod billing_events;
 pub mod providers;
 pub mod subscription_usage_meters;
 pub mod subscription_usages;