Update or replace djangorestframework-xml

[Jawayria]

We use the package djangorestframework-xml in edx/course-discovery, edx/edx-enterprise, edx/edx-platform, edx/enterprise-catalog. It hasn't yet added support for Django3.2. Please follow the guidance in https://openedx.atlassian.net/wiki/spaces/AC/pages/3036972032/Handling+Outdated+Dependencies to resolve the problem this poses for the Open edX Django 3.2 upgrade.

[jramnai]

@jmbowman, I am looking into this one. Reference PR - #56

[natabene]

@jramnai Thanks so much for looking into this, I appreciate. Please update here once your PR merges. I will assign this to you.