fixing a flaky test

Author: igorcosta

tests/ui/UserMessage.test.tsx

@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import { describe, it, expect } from 'bun:test';
+import { describe, it, expect } from 'vitest';
 import React from 'react';
 import { render } from 'ink-testing-library';
 import { UserMessage } from '../../src/ui/ink/UserMessage.js';