Add missing update of last_prediction_refresh (#43483)

Fixes a regression introduced in
https://github.com/zed-industries/zed/pull/43284 where edit predictions
stopped being throttled at all 😬

Release Notes:

- N/A

Co-authored-by: Ben Kunkle <ben@zed.dev>

crates/zeta/src/zeta.rs

@@ -1123,7 +1123,6 @@ impl Zeta {
         zeta_project.next_pending_prediction_id += 1;
         let last_request = zeta_project.last_prediction_refresh;
 
-        // TODO report cancelled requests like in zeta1
         let task = cx.spawn(async move |this, cx| {
             if let Some((last_entity, last_timestamp)) = last_request
                 && throttle_entity == last_entity
@@ -1133,6 +1132,12 @@ impl Zeta {
                 cx.background_executor().timer(timeout).await;
             }
 
+            this.update(cx, |this, cx| {
+                this.get_or_init_zeta_project(&project, cx)
+                    .last_prediction_refresh = Some((throttle_entity, Instant::now()));
+            })
+            .ok();
+
             let edit_prediction_id = do_refresh(this.clone(), cx).await.log_err().flatten();
 
             // When a prediction completes, remove it from the pending list, and cancel