Fix "storage.deleteCookies" partition test for iframe.

Differential Revision: https://phabricator.services.mozilla.com/D230696

bugzilla-url: https://bugzilla.mozilla.org/show_bug.cgi?id=1934045
gecko-commit: 484fd74c094b9a70fd4e4bf14633c31c82e856a6
gecko-reviewers: webdriver-reviewers, whimboo

webdriver/tests/bidi/storage/delete_cookies/partition.py

@@ -132,7 +132,7 @@ async def test_partition_context_iframe(
     )
 
     result = await bidi_session.storage.delete_cookies(partition=frame_partition)
-    await assert_partition_key(bidi_session, actual=result["partitionKey"], context=new_tab["context"])
+    await assert_partition_key(bidi_session, actual=result["partitionKey"], context=iframe_context["context"])
 
     await assert_cookies_are_not_present(bidi_session, frame_partition)