collab: Remove unused RateLimiter (#29343)

This PR removes the `RateLimiter` from the collab codebase, as it is no
longer used.

Release Notes:

- N/A

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

@@ -1,58 +0,0 @@
-use super::*;
-use crate::db::tables::rate_buckets;
-use sea_orm::{ColumnTrait, EntityTrait, QueryFilter};
-
-impl Database {
-    /// Saves the rate limit for the given user and rate limit name if the last_refill is later
-    /// than the currently saved timestamp.
-    pub async fn save_rate_buckets(&self, buckets: &[rate_buckets::Model]) -> Result<()> {
-        if buckets.is_empty() {
-            return Ok(());
-        }
-
-        self.transaction(|tx| async move {
-            rate_buckets::Entity::insert_many(buckets.iter().map(|bucket| {
-                rate_buckets::ActiveModel {
-                    user_id: ActiveValue::Set(bucket.user_id),
-                    rate_limit_name: ActiveValue::Set(bucket.rate_limit_name.clone()),
-                    token_count: ActiveValue::Set(bucket.token_count),
-                    last_refill: ActiveValue::Set(bucket.last_refill),
-                }
-            }))
-            .on_conflict(
-                OnConflict::columns([
-                    rate_buckets::Column::UserId,
-                    rate_buckets::Column::RateLimitName,
-                ])
-                .update_columns([
-                    rate_buckets::Column::TokenCount,
-                    rate_buckets::Column::LastRefill,
-                ])
-                .to_owned(),
-            )
-            .exec(&*tx)
-            .await?;
-
-            Ok(())
-        })
-        .await
-    }
-
-    /// Retrieves the rate limit for the given user and rate limit name.
-    pub async fn get_rate_bucket(
-        &self,
-        user_id: UserId,
-        rate_limit_name: &str,
-    ) -> Result<Option<rate_buckets::Model>> {
-        self.transaction(|tx| async move {
-            let rate_limit = rate_buckets::Entity::find()
-                .filter(rate_buckets::Column::UserId.eq(user_id))
-                .filter(rate_buckets::Column::RateLimitName.eq(rate_limit_name))
-                .one(&*tx)
-                .await?;
-
-            Ok(rate_limit)
-        })
-        .await
-    }
-}