Is your feature request related to a problem? Please describe.
We're in the process of starting to use CLA assistant to check for CLA for contributions to Python.

1. The page: https://www.python.org/psf/contrib/ should be updated to reflect the new process.
   Currently it contains links to the PSF contribution form (https://www.python.org/psf/contrib/contrib-form/)

• It should be updated to point to our instance of CLA assistant:

https://psf-cla-assistant-staging.herokuapp.com/python/cpython (TODO: replace with correct URL)

1. Under new CLA process, we will only be accepting the contributions under the Apache 2.0 license.

• The Academic free license should be removed from the page

1. Under the "Submission instructions" heading, the link to online form points to the legacy cla form.

• It should be updated to the new CLA assistant page
• Provide a PDF version of the form.

1. The legacy cla form can be removed.

• Remove https://www.python.org/psf/contrib/contrib-form/

Additional context

See the Migrating to CLA Assistant core-workflow project.

See also devguide PR outlining how to sign the CLA under the new process: python/devguide#490