Summary:
Switches to the `nullthrows` package instead of using `fbjs/lib/nullthrows`.
The version of `nullthrows` in `fbjs` is outdated and already missing features that exist in the standalone `nullthrows` package.
Also, this mitigates the inevitable collision between `nullthrows` (as a Haste module) and `nullthrows` (as a `node_modules` dependency).
Reviewed By: zertosh
Differential Revision: D9733178
fbshipit-source-id: 1b589d48c1ed57cebf2088b796ad72e212534c0a
5023b105e4