refactor: remove unnecessary import (#15)

Author: larkee

tests/system/test_system.py

@@ -23,7 +23,6 @@
 import unittest
 import uuid
 
-import pytest
 import grpc
 from google.rpc import code_pb2
 
@@ -387,8 +386,8 @@ def test_table_not_found(self):
         with self.assertRaises(exceptions.NotFound):
             temp_db.create()
 
-    @pytest.mark.skip(
-        reason=(
+    @unittest.skip(
+        (
             "update_dataset_ddl() has a flaky timeout"
             "https://github.com/GoogleCloudPlatform/google-cloud-python/issues/"
             "5629"