[TrivialFix]Remove unnecessary value taking

This is to remove unnecessary value taking for code clean.

Change-Id: I570218f617c49d710c24ecf0d5ca4211835ecaa8
diff --git a/tempest/api/compute/admin/test_quotas.py b/tempest/api/compute/admin/test_quotas.py
index 1aa9227..5894e80 100644
--- a/tempest/api/compute/admin/test_quotas.py
+++ b/tempest/api/compute/admin/test_quotas.py
@@ -157,8 +157,7 @@
 
     def _restore_default_quotas(self, original_defaults):
         LOG.debug("restoring quota class defaults")
-        self.adm_client.update_quota_class_set(
-            'default', **original_defaults)['quota_class_set']
+        self.adm_client.update_quota_class_set('default', **original_defaults)
 
     # NOTE(sdague): this test is problematic as it changes
     # global state, and possibly needs to be part of a set of