tests: fix apparently erroneous localhost delegation.

The stack delegates to localhost, which has ansible_python_interpreter
set.

tests/ansible/integration/delegation/stack_construction.yml

@@ -331,9 +331,7 @@
           out.result == [
               {
                   'kwargs': {
-                      'python_path': [
+                      'python_path': None
-                          hostvars['cd-normal'].local_env.sys_executable
-                      ],
                   },
                   'method': 'local',
               },