remove `requestOptions.request` as it should not be needed

I implemented #1220 b/c I was having getting `jest.mock()` to work w/ our packages (any package really), however, I now have it working, and I think that, or `vi.mock()` is a much better option that this library providing a way to mock the low-level `request()` function.

As this will be a breaking change, it should be part of the v5 release.