We don't actually use this anywhere, so let's remove it.

https://github.com/facebook/react/blob/f1d00156df5453bc62bd5668fefdcac4ca67e90e/src/renderers/shared/fiber/ReactFiberScheduler.js#L1504-L1512
const root = roots.get(rootID);
    if (root) {
      NoopRenderer.updateContainer(null, root, null, () => {
        roots.delete(rootID);
        rootContainers.delete(rootID);
      });
    }
  },
  findInstance(
    componentOrElement: Element | ?React$Component<any, any>,
  ): null | Instance | TextInstance {
    if (componentOrElement == null) {
      return null;
    }
    // Unsound duck typing.
    const component = (componentOrElement: any);
    if (typeof component.id === 'number') {
      return component;
    }
    const inst = ReactInstanceMap.get(component);
    return inst ? NoopRenderer.findHostInstance(inst) : null;
  },
  flushDeferredPri(timeout: number = Infinity): Array<mixed> {
    // The legacy version of this function decremented the timeout before
    // returning the new time.
    // TODO: Convert tests to use flushUnitsOfWork or flushAndYield instead.
    const n = timeout / 5 - 1;
    let values = [];
    for (const value of flushUnitsOfWork(n)) {
      values.push(...value);