Update zed_llm_client to v0.8.1 (#30433)

This PR updates the `zed_llm_client` crate to v0.8.1.

The name of `Plan::Free` changed to `Plan::ZedFree` in this version.

Release Notes:

- N/A

crates/collab/src/db/tables/billing_subscription.rs

@@ -99,7 +99,7 @@ impl From<SubscriptionKind> for zed_llm_client::Plan {
         match value {
             SubscriptionKind::ZedPro => Self::ZedPro,
             SubscriptionKind::ZedProTrial => Self::ZedProTrial,
-            SubscriptionKind::ZedFree => Self::Free,
+            SubscriptionKind::ZedFree => Self::ZedFree,
         }
     }
 }