Remove unused import from combining domains

Since we no longer make multiple calls we don't need both calls from
unit testing anymore

tests/lib/openstack_api/test_openstack_roles.py

@@ -1,4 +1,4 @@
-from unittest.mock import MagicMock, call
+from unittest.mock import MagicMock
 import pytest
 
 from enums.user_domains import UserDomains