Fix test_create_default_bucket: check None instead of NotFound (#36814)

Author: aIbrahiim

sdks/python/apache_beam/io/gcp/gcsio_integration_test.py

@@ -261,8 +261,8 @@ def test_create_default_bucket(self, mock_default_gcs_bucket_name):
       except NotFound:
         pass
     time.sleep(WAIT_BUCKET_PROPAGATION_SECONDS)
-    with self.assertRaises(NotFound):
-      self.gcsio.get_bucket(overridden_bucket_name)
+    bucket_after_delete = self.gcsio.get_bucket(overridden_bucket_name)
+    self.assertIsNone(bucket_after_delete)
 
 
 class GcsIOReadGzipTest(unittest.TestCase):