Update testing.md (#2409)

- added missing import

Author: itoxiq

docs/openapi-fetch/testing.md

@@ -45,7 +45,7 @@ test("my request", async () => {
 import { http, HttpResponse } from "msw";
 import { setupServer } from "msw/node";
 import createClient from "openapi-fetch";
-import { afterEach, beforeAll, expect, test } from "vitest";
+import { afterEach, beforeAll, afterAll, expect, test } from "vitest";
 import type { paths } from "./my-openapi-3-schema"; // generated by openapi-typescript
 
 const server = setupServer();