Revert "fix: align tubco onboarding models with deployed schema"

This reverts commit 054558fda2.

backend/workflows/tests/test_onboarding_flow.py

@@ -49,8 +49,6 @@ class OnboardingFlowTests(TestCase):
         self.assertEqual(obj.full_name, 'Max Mustermann')
         self.assertEqual(obj.onboarded_by_email, f'requester@{self.company_domain}')
         self.assertEqual(obj.onboarded_by_name, 'Mia Beispiel')
-        self.assertEqual(obj.approval_released_by_name, '')
-        self.assertIsNone(obj.approval_released_at)
         mock_delay.assert_called_once_with(obj.id)
 
     @patch('workflows.views.process_onboarding_request.delay')