Don't update active completion for editors that are not focused (#9904)

Release Notes:

- N/A

crates/copilot_ui/src/copilot_completion_provider.rs

@@ -764,6 +764,7 @@ mod tests {
             multibuffer
         });
         let editor = cx.add_window(|cx| Editor::for_multibuffer(multibuffer, None, cx));
+        editor.update(cx, |editor, cx| editor.focus(cx)).unwrap();
         let copilot_provider = cx.new_model(|_| CopilotCompletionProvider::new(copilot));
         editor
             .update(cx, |editor, cx| {