Replace instances of 'url' function with 're_path'

[calvh]

url is deprecated since django 3.1

https://docs.djangoproject.com/en/3.2/ref/urls/#url

[ryumada]

This was the error I found too while doing the sixth tutorial. I fix it by replace the url into re_path.

the import:
https://github.com/ryumada/python-djangorestframework-tutorial/blob/220c7f3a4cb0bc3c553b50e3409bdc2f5bfb358f/snippets/urls.py#L1

using re_path instead:
https://github.com/ryumada/python-djangorestframework-tutorial/blob/220c7f3a4cb0bc3c553b50e3409bdc2f5bfb358f/snippets/urls.py#L13-L15

Here is the discussion I've found:
https://stackoverflow.com/questions/70319606/importerror-cannot-import-name-url-from-django-conf-urls-after-upgrading-to

[auvipy]

contributions are welcome