Delete no meaningful definition

  fetched_creds is defined in the following code, above definition
is no meaningful, just delete it.

Change-Id: Ie2984d694d3555a23fb012afe5982ffb99e054ac
diff --git a/tempest/api/identity/v2/test_ec2_credentials.py b/tempest/api/identity/v2/test_ec2_credentials.py
index 3c379f0..8f493aa 100644
--- a/tempest/api/identity/v2/test_ec2_credentials.py
+++ b/tempest/api/identity/v2/test_ec2_credentials.py
@@ -51,7 +51,6 @@
     def test_list_ec2_credentials(self):
         """Get the list of user ec2 credentials."""
         created_creds = []
-        fetched_creds = []
         # create first ec2 credentials
         creds1 = self.non_admin_users_client.create_user_ec2_credential(
             self.creds.user_id,