Fix typo

Author: rayluo

tests/test_mi.py

@@ -141,7 +141,7 @@ def test_unified_api_service_should_ignore_unnecessary_client_id(self):
             {"ManagedIdentityIdType": "ClientId", "Id": "foo"},
             token_cache=TokenCache()))
 
-    def test_app_service_error_should_be_normalized(self):
+    def test_sf_service_error_should_be_normalized(self):
         raw_error = '''
 {"error": {
     "correlationId": "foo",