collab: Exempt staff from LLM usage limits (#19836)

This PR updates the usage limit check to exempt Zed staff members from
usage limits.

We previously had some affordances for the rate limits, but hadn't yet
updated it for the usage-based billing.

Release Notes:

- N/A

crates/collab/src/llm.rs

@@ -449,6 +449,10 @@ async fn check_usage_limit(
     model_name: &str,
     claims: &LlmTokenClaims,
 ) -> Result<()> {
+    if claims.is_staff {
+        return Ok(());
+    }
+
     let model = state.db.model(provider, model_name)?;
     let usage = state
         .db
@@ -513,11 +517,6 @@ async fn check_usage_limit(
     ];
 
     for (used, limit, usage_measure) in checks {
-        // Temporarily bypass rate-limiting for staff members.
-        if claims.is_staff {
-            continue;
-        }
-
         if used > limit {
             let resource = match usage_measure {
                 UsageMeasure::RequestsPerMinute => "requests_per_minute",