Revert .issue-item wait in duplicate import test

The waitForDisplayed('.issue-item') was causing timeouts on CI when the
popup needed to fetch from the API (no seeded cache). The duplicate
detection reads from storage, not the rendered DOM, so the wait was
unnecessary. Rely on Mocha retry for intermittent BiDi flakiness.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: richardkmichael

tests/firefox/extension.spec.js

@@ -200,8 +200,6 @@ describe('Popup', function () {
 
     await browser.url(popupUrl());
     await waitForPopupLoaded();
-    // Ensure the seeded bookmark is rendered before testing import duplicate detection
-    await $('.issue-item').waitForDisplayed({ timeout: 10000 });
 
     const importBtn = await $('#import-btn');
     await importBtn.click();