doc: exercising module code locally: update cmd (#45697)

The documented way to execute module code locally wasn't always working:

    $ python ./lib/ansible/modules/files/file.py <<< '{"ANSIBLE_MODULE_ARGS": {}}'
    Traceback (most recent call last):
      File "./lib/ansible/modules/files/file.py", line 177, in <module>
        from ansible.module_utils.basic import AnsibleModule
      File "~/ansible/lib/ansible/module_utils/basic.py", line 78, in <module>
        import tempfile
      File "~/ansible/lib/ansible/modules/files/tempfile.py", line 69, in <module>
        from tempfile import mkstemp, mkdtemp
    ImportError: cannot import name 'mkstemp'

docs/docsite/rst/dev_guide/developing_modules_general.rst

@@ -211,7 +211,7 @@ If you module does not need to target a remote host, you can quickly and easily
    development) activate it: ``$ . venv/bin/activate``
 -  Setup the environment for development: ``$ . hacking/env-setup``
 -  Run your test module locally and directly:
-   ``$ python ./my_new_test_module.py /tmp/args.json``
+   ``$ python -m ansible.modules.cloud.azure.my_new_test_module /tmp/args.json``
 
 This should return output something like this: