unskip test_workflow_chain()

Since the upgrade to celery 4, this test pass.

test/test_celerytask.py

@@ -19,7 +19,6 @@
 
 import collections
 import logging
-import unittest
 import time
 import os.path
 
@@ -153,7 +152,6 @@ class CeleryTaskTC(BaseCeleryTaskTC):
                                            terminate=True)
             self.assertFalse(os.path.exists(get_log_filename(task.task_id)))
 
-    @unittest.skipIf(celery.VERSION.major == 3, "not supported with celery 3")
     def test_workflow_chain(self):
         with self.admin_access.repo_cnx() as cnx:
             s = celery.signature