Revert "Adds preferences API and updates users to V1"

docs/en_us/platform_api/source/change_log.rst

docs/en_us/platform_api/source/conf.py

...platform_api/source/course_structure/course_structure.rst

docs/en_us/platform_api/source/enrollment/enrollment.rst

docs/en_us/platform_api/source/index.rst

docs/en_us/platform_api/source/mobile/course_info.rst

docs/en_us/platform_api/source/mobile/users.rst

docs/en_us/platform_api/source/mobile/video_outlines.rst

docs/en_us/platform_api/source/overview.rst

docs/en_us/platform_api/source/user/accounts.rst

docs/en_us/platform_api/source/user/endpoints.rst

docs/en_us/platform_api/source/user/index.rst

docs/en_us/platform_api/source/user/overview.rst

docs/en_us/platform_api/source/user/preferences.rst

openedx/core/djangoapps/user_api/accounts/views.py

openedx/core/djangoapps/user_api/preferences/views.py