PAP-10430: import act in sidebar test

ui/src/components/Sidebar.test.tsx

@@ -1,6 +1,6 @@
 // @vitest-environment jsdom
 
-import type { ReactNode } from "react";
+import { act, type ReactNode } from "react";
 import { flushSync } from "react-dom";
 import { createRoot } from "react-dom/client";
 import { QueryClient, QueryClientProvider } from "@tanstack/react-query";