Remove override of 'expected_error_codes' with defaults

'expected_error_codes' are filled with defaults error code[1]
in base class which is nothing but to fill required number
of error codes with 403.

Few tests override the 'expected_error_codes' with 403 itself which
is confusing and inconsistent with other tests.

This commit removes those default overridden values.

[1] https://github.com/openstack/patrole/blob/a6371ed510b318183e1c2cbafcc97bd85f6625f8/patrole_tempest_plugin/rbac_rule_validation.py#L286

Change-Id: If607755fc09c392566fffad8f46e5f37cd33c2d2
diff --git a/patrole_tempest_plugin/rbac_rule_validation.py b/patrole_tempest_plugin/rbac_rule_validation.py
index e6d1e80..32deb9f 100644
--- a/patrole_tempest_plugin/rbac_rule_validation.py
+++ b/patrole_tempest_plugin/rbac_rule_validation.py
@@ -110,7 +110,7 @@
         c) if both api_action1 and api_action2 fail, then the expected error
            code is the first error seen (404).
 
-        If an error code is missing from the list, it is defaulted to 403.
+        If it is not passed, then it is defaulted to 403.
 
     :param dict extra_target_data: Dictionary, keyed with ``oslo.policy``
         generic check names, whose values are string literals that reference