zeta: Fix completions not being marked as rated

Seems like #22171 accidentally removed this line.

Now it's back and completions are marked as rated again.

crates/zeta/src/zeta.rs

@@ -733,6 +733,7 @@ and then another
         feedback: String,
         cx: &mut ModelContext<Self>,
     ) {
+        self.rated_completions.insert(completion.id);
         telemetry::event!(
             "Inline Completion Rated",
             rating,