Aside from in the LMS, the `RequireJS-namespace.js` files are only used by the test runner. In the unit tests, we want `require` to be defined in the global context, so that tests can use it. We only care about undefining it in the LMS because that codebase is already written on the assumption that `require` is not defined in the global context, and we want to change the LMS codebase as little as possible.