Refs #32292 -- Made dbshell do not use 'postgres' database when service name is set.

Regression in dcb3ad3319.

tests/dbshell/test_postgresql.py

@@ -70,7 +70,7 @@ class PostgreSqlDbshellCommandTestCase(SimpleTestCase):
     def test_service(self):
         self.assertEqual(
             self.settings_to_cmd_args_env({'OPTIONS': {'service': 'django_test'}}),
-            (['psql', 'postgres'], {'PGSERVICE': 'django_test'}),
+            (['psql'], {'PGSERVICE': 'django_test'}),
         )
 
     def test_column(self):