* refactor: simplify bulk management enabling

Formerly, a course had to have bulk management enabled and have a master's
track. This painted us into a corner where we had to create a
workaround for enabling bulk management on non-master's track courses.
Instead, this relies only on an enabled flag from edx-platform (based on
a course waffle flag) which simplifies the enabling code here.

* feat: remove unneeded bulk management allow-list